Demona, known also as The Demon, is a female gargoyle. She was once a member of the Wyvern Clan and was Goliath's former mate, known to him at least as his Angel of the Night. She is now one of the Manhattan Clan's greatest enemies, and possibly the most dangerous gargoyle in the world.
Dominique Destine is her human alias.
Demona was hatched in the year 938. By 971, she and Goliath were already falling in love with each other. However, the young Demona - at that time, known only as "Angel of the Night" or simply "Angel", pet names which Goliath had bestowed upon her - had already begun to develop the weaknesses that would lead her down a dark path to come. Showing a strong interest in magic, she approached and secretly entered into the Archmage's service as his apprentice, in which role she served largely as a servant and errand-runner. He also taught her to read, and she in turn taught Goliath. The Archmage treated her harshly, dominating her by his threats, and she obeyed his commands out of fear. This reached its climax in 975, when the Archmage commanded her to steal the Phoenix Gate from Princess Elena.
Just after Demona stole the Gate, an older version of herself appeared with a duplicate Phoenix Gate, and whisked them both away to the year 994, accompanied by an older version of Goliath (both from the year 1995). There, the older Demona showed the younger one the aftermath of the Wyvern Massacre and Goliath's petrified form on the battlements, urging her to use the Phoenix Gate to avert this disaster and destroy the humans. The younger Demona was horrified at her future self's coldness and callousness, and refused to become like her, but was also disturbed at what she had seen. The Goliath from the future did what he could to comfort her, urging her to not worry about this catastrophe but to remain true to her love.
The younger Demona then returned herself and the two time travelers to 975, where she hid the Phoenix Gate from the Archmage, pretending that she had lost it. The Archmage, furious, cast her off as his apprentice then and there. Afterward, Demona and Goliath attended Prince Malcolm's wedding; she broke the Phoenix Gate in half there, giving one half of it to him as a token of her love, while keeping the other half for the same purpose. ("Vows") Demona lost her virginity to Goliath (and he to her) that night. 
Demona grew older and became one of the greatest warriors of the Clan, protecting the humans of the Castle but remaining troubled over the vision of the future she saw and becoming more and more angry by the humans' treatment of her and her kind. In 984, her former teacher the Archmage tried to take over Wyvern but was defeated. In a last attempt to kill Prince Malcolm, the human leader at the time, the Archmage shot him with a poisonous dart which only a spell from the Grimorum Arcanorum could cure. The Clan's leader, known later as Hudson was entrusted to bring back the book and he decided to take Goliath, by this point the Clan's second-in-command, and Demona with him. Together they tracked the Archmage to a cave and were able to retrieve the book and return it to Castle Wyvern, saving Prince Malcolm's life. Demona expressed many misgivings over Hudson's advancing age and ability to lead, and it was this and Hudson's own feelings on the matter that convinced Hudson to step down and allow Goliath to lead. ("Long Way To Morning") In truth, Demona wanted this for Goliath, and herself very much and Goliath soon made her his second-in-command. One member of the clan, Demona's rookery sister Hyppolyta, disagreed with this turn of the events and felt Goliath was not the best choice for leader. Demona often argued with Hyppolyta about this.
Some time before 994, Demona got her ears pierced and started wearing earrings.
By 994, Demona had finally had enough of the constant ingratitude of Princess Katharine, Prince Malcolm's heir, and her human subjects towards the clan, and decided, with the Captain of the Guard, to betray the humans to Hakon and his Vikings. The two plotters urged Goliath to take the entire clan and drive the Vikings away from the castle, intending to have Hakon capture Castle Wyvern in the gargoyles' absence at night. But Goliath, unwilling to leave the castle undefended, only took Hudson with him ("Awakening" Part One). The Captain, desperate to have the plan succeed, decided to have Hakon attack during the daytime instead. Demona was alarmed, knowing that in the daytime, the clan would be trapped in its stone sleep and defenseless. She dared not warn the rest of the gargoyles, however, for fear that if she did so, she might have to reveal her part in the conspiracy, and so fled alone to hide upon the beach.
She awakened that night, and returned to find her clan destroyed by the Vikings. Horrified and grief-stricken, she hid herself when Goliath returned to the castle, too afraid to face him. By the time that she re-emerged from hiding, Goliath and the other survivors had already been put to sleep (seemingly forever) by the Magus.
Looking up at her mate's petrified form, Demona cried out, "What have I - what have they done to you?" In that moment, her mood changed from grief to anger and hatred, burying the guilt that she felt over having contributed to the destruction of her clan underneath her rage at the humans, blaming them for her woes so that she could avoid facing her own responsibility for them.
She saw below Princess Katharine, the Magus, and Tom loading the rookery eggs on the cart and driving away with them, but made no effort to go after them as she was unable to "face" the eggs. Instead, she kissed the stone Goliath one last time, and glided away, sending herself into exile.  ("City of Stone Part One")
Coming to a nearby farm, she raided the barn for food. The farmer's young son Gillecomgain, hearing the commotion from the animals, came to investigate, and Demona promptly slashed him across his face with her claws, scarring him, in her anger. This proved a fatal action for her, for Gillecomgain vowed revenge upon Demona and her race, and grew up to become the first Hunter, an enemy both to Demona and to all gargoyles.
Demona continued to wander about Scotland, attacking any human who got in her way and stealing food to survive. By 997 other rogue gargoyles, the survivors of clans that had been destroyed by the humans, including Demona's Second, joined her, and by 997, she was the leader of a new clan, if a rather ragtag one, which turned to banditry. Learning from the lessons of the past, she arranged for the clan to sleep in different places, so if one "cell" was discovered and destroyed the rest would live on.
Shortly after Brooklyn time traveled to 997, the entire Sruighlea Cell of Demona's clan had been massacred by King Constantine and Gillecomgain. Amid their remains, Demona discovered a wanted poster left behind for Mary and Finella and discovered that they possessed the Grimorum. Brooklyn later approached her on behalf of Mary, Finella, and the Grim asking for help against Constantine. Seeing an opportunity to seize the Grimorum, Demona agreed. Although she planned to destroy both armies and use the Grimorum to bring Scotland to its knees. ("The Gate"; "Tyrants")
In the midst of the battle, Brother Valmont used the Grimorum to rain down a storm of magical arrows. Demona seized the book to reverse his spell, if not the consequences. After Constantine was defeated, the phoenix appeared to spirit Brooklyn away. Knowing he couldn't let Demona keep the Grimorum, Brooklyn offered to hold the book for her while she reached for her half of the Phoenix Gate, letting her believe she needed it to control the Phoenix. ("Phoenix")
As the years passed, the grown-up Gillecomgain, as the Hunter, had become one of Demona's worst enemies, and a danger to all the surviving gargoyles left in Scotland as well. ("City of Stone" Part One)
In 1020, the Weird Sisters were assigned the task of watching over Demona and Macbeth by the Archmage, and set to work at once ("Avalon Part Two"). They persuaded Demona to attack Gillecomgain at Castle Moray, when he went there on Prince Duncan's orders to assassinate Findlaech, and there she met Macbeth for the first time, and actually saved his life, although having to allow the Hunter to escape in order to so do. ("City of Stone" Part One)
Twelve years later, the Sisters again persuaded Demona to fight Gillecomgain at Castle Moray by Macbeth's side. This time, she slew the Hunter, and Macbeth saved her life, for which she grudgingly thanked him, hoping that their dealings were now at an end ("City of Stone" Part Two).
They were not. When Duncan finally decided to destroy Macbeth in 1040, he feared that Demona and her clan would aid Macbeth against him, and so attempted to destroy them as the Hunter. This backfired, however, for it helped force Macbeth and Demona into an alliance against Duncan as the common foe. All the same, Demona did not quite trust Macbeth, until the Weird Sisters appeared and made Demona this offer: if she would agree to the alliance with Macbeth, they would rejuvenate her. Demona, (by now the gargoyle equivalent of 51 and prematurely aged by her strenuous living), agreed to this, and the Sisters caused her and Macbeth to switch ages (making Macbeth 51 and Demona the gargoyle equivalent of 35, the age that Macbeth was then). In so doing, they also made them both unaging and immortal, only able to die if one slew the other, although they did not mention this at the time.
With the aid of Demona and her clan, Macbeth overthrew Duncan in battle and became the new King of Scotland. He placed her clan under his protection, and declared her his primary advisor ("City of Stone" Part Three). Following his coronation in 1040, Macbeth gave Demona her name, because he thought she fought like a demon. And for the next seventeen years, Demona could know peace and safety at last. Other gargoyles came to know about this new golden age between humans and gargoyles and flocked under her leadership and her clan grew in size. This peaceful and happy respite came to a tragic end in 1057, when a grown-up Canmore invaded Scotland with the help of the English, seeking to regain his father's throne and achieve his revenge. Demona and her clan valiantly fought against the English invaders, but in a private council, Bodhe urged Macbeth to cast off his alliance with the gargoyles, since (so Bodhe thought) the English were only invading Scotland because of their hatred for their kind and would go home if Macbeth abandoned Demona's clan.
Unfortunately, Macbeth did not immediately reject this advice, wishing to show his son Luach that "a wise king considers all his options, and then decides," and equally unfortunately, Demona, though not invited to the council, was secretly eavesdropping on it. Convinced that Macbeth would indeed betray her and her clan to the English, she decided to betray them first, and so abandoned Castle Moray on the eve of the final battle. Deprived of the gargoyles' aid, Macbeth was defeated by Canmore; however, Canmore had Demona's clan destroyed as well, probably because as an army they were all together and thus easily smashed. Demona was alone once again, the last gargoyle alive in Scotland (or so she thought), and eventually she fled for other parts of the world. ("City of Stone" Part Four)
The period of her life between 1057 and 1994 is far more sketchily-recorded than that between 994 and 1057. She was possibly involved in many watershed events in European and American history.
Demona roamed most of the world, pursued both by Macbeth (who first hunted her to seek revenge and later simply to end his long life) and by a new line of Hunters descended from Canmore, who had somehow learned of her survival and chosen to hunt her down, because of a "little mishap" with Canmore and his son, Donald . Growing increasingly bitter towards humans, she finally decided that she must destroy them all, partly as the only means of ensuring survival for herself and what little remained of her race, partly as a means of gaining her revenge. Demona, likely to have already been living in France in the early 15th century, took her first step towards this goal when she stole the Medici Tablet in Florence in the year 1495, upon which was engraved the Fulfillment Spell. ("Hunter's Moon Part Two")
In 1920, Demona journeyed to Paris to locate the Praying Gargoyle and used it to animate every gargoyle statue in Paris for the express purpose of murdering every human in the city. She was foiled by Fiona Canmore and Team Atlantis, and at the end, her life was saved by Joshua Sweet. Though the Praying Gargoyle was destroyed during her defeat, she was able to retrieve the Atlantean crystal inside it and moved it to holy ground where in sixty years it would regenerate. ("The Last")
In 1980, she returned to Notre Dame Cathedral in Paris and regained possession of the relic, killing the Hunter Charles Canmore in the process ("Hunter's Moon Part Three). The Weird Sisters watched over her and Macbeth all this time, and twice intervened in her life, under as yet unchronicled circumstances. ("Avalon" Part Two)
At some point between 1980 and 1994, Demona met David Xanatos thanks to some maneuvering behind the scenes by Brooklyn, Finella, and Mary, with Owen/Puck handling the actual introductions, and the two of them formed an alliance for the purpose of reviving Goliath and his clan from their stone sleep, each for personal reasons. Partnering with Xanatos, Demona once again had access to the Grimorum Arcanorum, in which she likely read the Magus's account written in the back pages. After Xanatos moved Castle Wyvern to the top of the Eyrie Building, thus breaking the Magus' spell, Demona revealed herself to the awakened clan, pretending that she had been under the Magus' spell. She helped dupe Goliath into making the raid on Cyberbiotics, but in the course of it, revealed to him the full depths of her bitterness, destroying Fortress-1 in order to kill as many humans as possible. When a horrified Goliath refused to join her in her crusade against humanity, she tried to kill him, but Elisa Maza saved Goliath's life, in the process making an enemy of Demona ("Awakening" Parts Two, Three and Four).From that point on, Demona attempted to either convert the gargoyles to her viewpoint, or, if she could not accomplish that, to destroy them. Among other stratagems, she tricked Brooklyn into helping her temporarily turn Goliath into a mindless zombie under her control, created the cybernetic gargoyle Coldstone, summoned Puck for the purpose of getting rid of all the humans in New York (which he didn't fulfill), and even tricked Goliath into yielding up to her his piece of the Phoenix Gate, so that she could go back in time to 975 and meet with her younger self, just as she had already done from her younger self's perspective. ("Temptation"; "Reawakening"; "The Mirror"; "Vows") Her first round of schemes after Goliath and his clan's awakening climaxed when she placed a curse over the humans in New York, causing them to turn to stone during the night so that she could smash them at her leisure. This curse was foiled, not only by an alliance between Goliath and Xanatos (thus ending her alliance with him), but also the unexpected intervention of first Macbeth, and then the Weird Sisters ("City of Stone" Parts I-IV).
The Sisters took Demona and Macbeth away with them, and used them to first steal the Grimorum Arcanorum, Eye of Odin, and Phoenix Gate from the clock tower, and next to attack the Avalon Clan. ("High Noon"; "Avalon" Part Two) After the defeat of the Archmage's forces, the Sisters lifted their hold over Demona and Macbeth, and caused them to forget everything that they had undergone while the Sisters had enchanted them, after which the Avalon Clan sent them away into the outside world ("Avalon" Part Three).
Avalon brought Demona and Macbeth to Paris, where Demona met and fell in love with Thailog. The two gargoyles used their combined wealth to set up Nightstone Unlimited, and afterward plotted to add to their fortune by Demona marrying Macbeth in her human form as Dominique Destine (she presented herself as a good Catholic French girl), then afterward locking him up, faking his death, and inheriting his wealth as his "widow". Thailog's real plan, however, was to trick the two into killing each other so that he could obtain all their money for himself. Fortunately, the Avalon World Tour also brought Goliath, Elisa, Angela, and Bronx to Paris, and they were able to foil Thailog's scheme and save Demona and Macbeth's lives. It was on that occasion that Demona first saw her daughter Angela (having no memory of their encounter on Avalon). ("Sanctuary")
Returning to New York with Thailog, Demona learned from Sevarius that Angela was her biological daughter. She decided to recruit Angela to her cause, as well as setting up a fresh clan for herself, by letting herself be captured by the gargoyles and imprisoned in the Labyrinth, where she arranged for the cloning of Hudson and the Trio, and did all that she could to subvert Angela over to her side, without success. Demona, Thailog, and the Clones then captured the clan, but when Thailog tried to kill Angela, Demona discovered that she had come to care about her daughter and turned on Thailog, freeing the Gargoyles and telling Goliath to "save our daughter!" ("The Reckoning")
Not long afterward, Demona used her resources at Nightstone Unlimited to complete the scheme that the Medici Tablet and Praying Gargoyle had begun, Operation Clean Slate, by employing Sevarius to create the CV-1000 Carrier Virus. On the night of the Hunter's Moon, in St. Damien's Cathedral, she used the Fulfillment Spell engraved on the Medici Tablet to merge the carrier virus with a case of D/I-7 detergent that she had stolen from Xanatos, creating a powerful plague designed to destroy all intelligent life on the planet, the Praying Gargoyle's magic becoming invoked to protect gargoyles from the plague. Fortunately, when Demona revealed her plan, Goliath intervened at the last moment to destroy the Praying Gargoyle, forcing Demona to abandon her plan. She managed to escape St. Damien's Cathedral, however. ("Hunter's Moon" Parts One, Two, and Three)
After her new personal assistant, Robyn Correy was revealed to be a Hunter and taken into custody, Demona decided to lie low as she is paranoid that Robyn may have blown her cover to the authorities. Demona has yet to return to Nightstone Unlimited, but she still sees the advantages of it. 
On Halloween, 1996, Demona returned to St. Damien's Cathedral to retrieve the crystal from the shattered remains of the Praying Gargoyle. ("Invitation Only")
Despite the foiling of her scheme, Demona will continue to plot the destruction of humanity with considerable bitterness. Altering the clan to suit her vision of what it should be like will still be a major goal. Although Angela will try, presumably unsuccessfully, to turn Demona from her destructive course.
When the Space-Spawn invade Earth in 2198, however, Demona is faced with an even greater enemy to her kind than humans, and so accepts Samson's invitation to join the Resistance, making use of her assets (such as her knowledge of magic and her ability to turn into a human in the daytime). However, Demona is uncertain as to whether she will be able to fight on the side of the angels for long. The rest of the Resistance distrusts her as well, and initially she does not get along well with anyone.  This may be her last chance at redemption... or her final opportunity to annihilate the human race. 
At some point in the war against the Space-Spawn, Demona will join Nokkar, Zafiro, LXM-1057, and Guardian by going into outer space to hit the Space-Spawn in their own home. Demona would potentially look like the Demona of "Future Tense" 
Greg Weisman has hinted that eventually she will indeed have an epiphany, learn that she was responsible for her own misery and suffering, and undergo some sort of change of heart and/or possibly go a little mad.  He has also said that she will have two more great loves, but their identities are as yet unknown.  Possibly even three more great loves. 
First and foremost, Demona is her own worst enemy. She has spent a thousand years alone, and that loneliness was a huge factor in creating the present day Demona. It has affected her to the point where, for a multitude of reasons, she even chose "ALONE" to be her access code during the climax of "City of Stone."
At present, Demona continues to bitterly hate humans, and wants the entire species destroyed. But she hates some humans more than others, such as the Hunters, Macbeth, and especially, Elisa Maza. She is vaguely aware of the detective's feelings for Goliath and his for Elisa, and is utterly jealous (deep down, she loves the Goliath of her imagination, but the real thing is a disappointment to her).
Besides, Elisa simply does not live up to Demona's beliefs about humans all being evil, traitorous, and hostile towards gargoyles, and that worries her even more. She also has strong hatreds for the Canmore Hunters, who have hounded her so often, and Macbeth, whom she still blames for the destruction of her clan in 1057 and his ongoing attempts to kill her. Although, it is worth noting that in the DVD audio commentary for "City of Stone Part Four," Greg Weisman noted that Demona was "a little bit in love with [Macbeth]." 
Her relationship with Thailog had little to do with Thailog personally, and more to do with his resemblance to Goliath, the contrast in his personality, and her desire to be with someone she believed could share her worldview.The one general exception to hatred in her heart at present is Angela, whom she has strong feelings for, but which as yet have not been enough to turn her from her path. Even the biological connection matters to Demona, although she would never admit to it, as such a thing is a human trait, and atypical to her species.  She will be aware that Samson is her descendant.
While she is not fond of the Children of Oberon, she is not overtly hostile towards them either. An exception to this is the Weird Sisters, whom she despises, not for rational reasons but because they're someone else she can blame for her problems. 
During the Dark Ages, Demona and Desdemona were as "close as sisters who aren't actually as close as they think."  At present, Demona would love to bring Coldfire to her way of thinking, but failing that, Coldfire would fall into Demona's ever-increasing enemies list. 
Demona's hatred of humanity is still fueled in part by her repressed guilt. She knows deep down inside that she is responsible in part for the Wyvern Massacre, but is unwilling to consciously admit it, and perforce makes the human race her scapegoat, to avoid facing the blood on her hands. She also continues to have a strong craving for power, hoping that when she destroys humanity and gargoyles subsequently rule the world, she will rule over them. In fact, the human name she chose for herself, Dominique Destine, stands for divine destiny. The Archmage taught her an appreciation of power. But it's doubtful she'd acknowledge that influence .
As far as a gargoyle's religious beliefs are concerned, Demona is "probably lapsed - or at least inattentive." . She also didn't consider it a priority to hold a Wind Ceremony for the massacred Sruighlea Cell, opting instead for vengeance on the humans.
At CONvergence 2011's Sex In Animation panel, Greg indicated that another of the many, many reasons for Demona's disposition was centuries of sexual frustration. 
Demona is currently immortal and unaging thanks to the spell that the Weird Sisters placed upon her in 1040. This spell also ensures that she can only die if she kills Macbeth or he kills her. Demona can still be temporarily killed, or wounded, however. If Macbeth is close enough at the time that such an event happens, he will feel her pain - and vice versa, thanks to the magical link between them. The same may also apply to feelings of pleasure.At present, Demona turns into a human during the daytime thanks to a magical gift that Puck bestowed upon her, taking on human form at dawn and reverting back to a gargoyle at sunset. The process is very painful, and Demona's one consolation for this is that if Macbeth is close enough, he can share her pain. Whether Demona would produce eggs (as is usual for a gargoyle) or give birth to live offspring (like a human) would depend which of the two forms she was in at the time. Demona will still have this feature by 2198, although her human alias by that period is unknown to us as yet. Her human alias, at present, is Dominique Destine, the CEO of Nightstone Unlimited, though she abandoned Nightstone after the failure of Operation Clean Slate.
Demona is a cunning and resourceful opponent, and a good fighter. However, her anger and hatred have a tendency to interfere with her plans; she will in the heat of battle make the mistake of using her laser cannon as a club rather than firing it, for example, and she will often alienate her allies or betray them, thus losing their assistance permanently. This has, fortunately, resulted in Demona's efforts to destroy humanity all failing.
Demona is also very mono-focused on her goals. She has no hobbies or interests, and focuses her efforts on research, study, practicing her sorcery, making investments, and other steps toward her goal. She also prefers to get a few hours of sleep during the day as Dominique, rather than sleep at night (and although Puck's spell of transformation compensates somewhat, the lack of sleep still doesn't improve her mental outlook).  And, according to Greg Weisman at the 2006 Blue Mug-a-Guest, Dominique "sleeps in the nude."
Physically, Demona is an attractive female gargoyle with a shock of red hair and pale blue skin. She is usually armed with a mace or a particle beam cannon or both. Her human form is that of an attractive red-haired, green-eyed woman, with a striking resemblance to her gargoyle form (close enough, in fact, that the musculoskeletal structure of her human head and her gargoyle head, according to a computer program of Robyn Canmore's, are virtually identical). As Dominique, she also keeps her fingernails trimmed to long, sharp points, giving her a slightly off-putting appearance as if she's not all human. Like all female gargoyles, her eyes glow red when she is angered, however, even as a human, if she gets angry enough, Puck's spell of transformation may glitch and her eyes will glow.
She usually wears a gold tiara, a pair of earrings, an armband and an anklet as decorative jewelry. She allowed Lexington to use one of her gold armbands to divert the electrical current of the bars in the cell of the Hunters' Airship so that they could escape, but replaced the armband with another soon afterward. She also seems to favor midriff bearing halter tops that hang off of one shoulder. Although, in 1920, she wore a pair of gauntlets on her forearms.
Ironically, Demona's character is a lot closer to William Shakespeare's Lady Macbeth than Gruoch was. As Lady Macbeth goads her husband into killing the elderly King Duncan, and taking his throne, Demona urges Goliath to seize leadership of the clan from Hudson. Unlike the Macbeth of the play, Goliath does no such thing, however, Hudson steps down and Goliath takes his place with Demona becoming second-in-command.
Adding to the irony, Demona briefly marries Macbeth in Paris. On top of this, in the unmade "The Weird Macbeth" story, several members of the cast would have been trapped by the Weird Sisters in a production of Shakespeare's "Macbeth" with Demona in the role of Lady Macbeth.
Demona has never had any biological children other than Angela, and never will  . However, considering both Puck's gift and her immortality, Greg Weisman has been asked about a hypothetical pregnancy multiple times, and he has theorized that if Demona were to become pregnant, the child would transform inside her as the sun rises and sets and feel the pain of her transformations . The species of said child would depend on the timing of her pregnancy, but most likely, Demona would lay an egg, before "Dominique" had the chance to come to full term . Of course, it's also possible that she would miscarry . But, on the huge and very unlikely assumption that "Dominique" would choose to have sex, "she's smart enough, even as a human, to use birth control" 
938. March. Hatches at Wyvern Hill.
984. Battles the Archmage with Goliath and Hudson. Hudson abdicates leadership of the clan and makes Goliath the new leader. Sometime between now and 994, Demona becomes Goliath's second-in-command. ("Long Way to Morning")
994. October 1. Wyvern Massacre. Demona survives by hiding away from the castle. She hides from Goliath and Hudson. Returning later, she finds the survivors of the clan frozen in stone sleep and Princess Katharine, the Magus, and Tom, leaving with the clan's eggs. Demona leaves Castle Wyvern. She later attacks the young Gillecomgain. ("Awakening" Part One, "City of Stone" Part One)
995-1020 Sometime during these years, Demona's Clan is founded.
1020. Allies with Macbeth for the first time. ("City of Stone" Part One)
1032. Allies with Macbeth again to battle and slay Gillecomgain. ("City of Stone" Part Two)
August 14. Battles alongside Macbeth against Duncan. Duncan defeated. ("City of Stone" Part Three)
September 29. Macbeth crowned High King of Scotland. He makes Demona his primary adviser. ("City of Stone" Part Three)
1980-1994. Sometime during these years, Demona allies with Xanatos.
1994. October 4. Remaining survivors of the Wyvern Clan awaken. ("Awakening" Part Two)
October 6. Reunites with Goliath and the clan. ("Awakening" Part Four)
November 12. Obtains the stolen Grimorum Arcanorum from Brooklyn. Casts spell on Goliath to enslave his mind and escapes with some pages of the Grimorum. ("Temptation")
1995. January 20-21. Attempts to poison Elisa Maza. Battles Hudson and Goliath and flees. ("Long Way to Morning")
September 28. Summons Puck, who first changes all the humans in Manhattan into gargoyles, then turns the Manhattan Clan into humans. Before departing, Puck casts a spell on Demona that transforms her into a human during the day. ("The Mirror")
November 6. Attends Xanatos and Fox's wedding. Obtains Goliath's half of the Phoenix Gate and transports the whole wedding party to Scotland, 975. ("Vows")
November 9. Tricks Xanatos into helping her broadcast as spell that turns all who see it to stone by day. ("City of Stone" Part One)
November 10. Smashes a number of stone humans. ("City of Stone" Part Two)
November 11. Attacked by Macbeth. Escapes. ("City of Stone" Part Two)
November 12. Sneaks into Castle Wyvern to sabotage Xanatos's plan to break her spell. Stopped by Macbeth. Confronted by the Weird Sisters, who take her and Macbeth away with them. ("City of Stone" Part Four)
November 13. In human form with Macbeth's help, Demona steals Coldstone from the clock tower, along with the Eye of Odin, the Grimorum Arcanorum, and the Phoenix Gate. Returns to gargoyle form at night and awakens Coldstone's "Iago" personality. ("High Noon")
November 14. Reveals her human form to Elisa and challenges her to rescue the captured Manhattan Clan. Fights Elisa at Belvedere Castle. Flees with Macbeth when "Othello" regains control of Coldstone. Begins to reject Weird Sisters' control over her, which is quickly reestablished. ("High Noon")
December 30. Under the spell of the Weird Sister, Demona and Macbeth attack the Avalon Clan and their new allies. Demona is defeated by Princess Katharine with assistance from humans and gargoyles of the Avalon and Manhattan clans. ("Avalon" Part Three)
1996. January 1. Is released from the Weird Sisters' spell along with Macbeth. The two are sent away from Avalon on a skiff by Goliath while both are still unconscious. ("Avalon" Part Three) The skiff arrives in Paris and Demona awakens. Seeing the unconscious Macbeth, she flees.
January 2. Meets Thailog and allies with him.
January 22. Marries Macbeth in her human identity of Dominique Destine. Meets Angela briefly. Departs with Thailog, unaware he attempted to let Macbeth kill her (or vice versa, with the same end result). ("Sanctuary")
May 7. Returns to Manhattan with Thailog and hires Dr.Sevarius, who confirms that Angela is her biological daughter.
July 15. Is imprisoned in the Labyrinth. First real meeting with Angela. ("The Reckoning")
October 13. Prevent Thailog from killing Angela and releases the Manhattan Clan and Talon. She disappears after a fire breaks out during her battle with Thailog. ("The Reckoning")
October 25. Destruction of the clock tower. The Manhattan Clan's existence is revealed to the world. ("Hunter's Moon" Part Three)
October 26. Attempts to cast a spell to destroy all humanity, but is stopped when Goliath destroys the Praying Gargoyle. She escapes. ("Hunter's Moon" Part Three)
October 31. Recovers a crystal that was contained within the Praying Gargoyle. ("Invitation Only") Like the statue itself, the crystal is Atlantean.
2198. Sometime this year or later, Demona joins Samson's resistance movement.
In Puck's nightmare vision of 2036, Demona joined the resistance against Xanatos, and eventually fell in love with its leader, Brooklyn. She begged Goliath to give Angela the Phoenix Gate so that she could use it to hide in time, Goliath refused. During the final assault on the Eyrie Pyramid, she was disintegrated by Xanatos in cyberspace. ("Future Tense")
In her Dominique Destine alias, Demona made use of several of the inmates at Ravencroft, including Dominic Dracon, Eddie Brock, John Jameson, and Cletus Kasady to uncover the head of the Spear of Destiny for her, and then united it with the spear-shaft (which she hired smugglers to bring her from Brazil), as the first step of her latest scheme. She used the Spear to restore the inmates' powers, once again transforming John Jameson into Colonel Jupiter, and re-bonding Eddie to his symbiote, unleashing Venom once more. She also gifted the serial killer, Kasady, with his own symbiote dubbing him Carnage.
She next allied herself with L. Thompson Lincoln alias Tombstone (the deposed Big Man of Crime), and offered him a chance to regain his empire in exchange for the services of the Tinkerer, who re-built five of Mysterio's Homunculi to assist her.
Later on, thanks to the escaped Dr. Octopus and Electro, she was able to enter Norman Osborn's vault at OsCorp and seize her true quarry, the Crown of Thorns. With both the crown and the spear, Demona planned to unleash Armageddon upon the human race, not to mention force Elisa Maza to joyfully commit suicide. But she was defeated by both Goliath and Spider-Man, and Dominique Destine found herself a patient at Ravencroft... at least until the sun went down.
After failing to destroy humanity on the night of the Hunter's Moon, Demona resurfaced and allied herself with a man known as the Assassin. She hired him to kill Goliath as part of a plan to convince Angela that Demona has reformed. However, the Assassin, who was working with the Quarrymen, ruined the deception, and Angela once again felt betrayed, something for which Demona felt true remorse. ("Generations")
As these non-canonical stories take place during and after the first season, Demona is allied with Xanatos, although loosely.("Fiends In High Places") She assists him in stealing DNA from Goliath and Elisa to create the composite clone, Venus. When she learns of a weapon that Xanatos is developing that can turn people to stone called the Medusa Device, she steals it but is soon defeated by Goliath.("Venus In Stone")("Venus Rising)
Next, she allied herself with the Triad, a Chinese crime syndicate who worshiped her as a goddess. They engaged in a scheme to use a lightning bolt to hatch a gargoyle egg that the Triad held in their possession for centuries... I know, I know, just go with it. This scheme was also foiled by Goliath.("Terror In Times Square")("The Egg And I")
It can safely be assumed that Demona was given all the dumplings and egg drop soup she could ask for. But I doubt her fortune cookies gave her any good news.
Behind the Scenes
Voice Actor: Marina Sirtis
Demona evolved from a gargoyle in the comedy development named Georgette. Though she wasn't the leader, Georgette was good at coming up with workable plans and pulling the other gargoyles tails out of the fire. Georgette was later promoted to leader and renamed "Dakota." She was smart and fearless, but ultimately a little too intense for a comedy series. In the final comedy development pitch, she was renamed "DeMona" and became the only gargoyle to side with the series' main villain. She survived into the final action-drama pitch as essentially the same character.
Other names suggested for Demona when Gary Krisel felt the name "Demona" was too on the nose were Angelica, Carve, Dagger , Shale, Slate, Malachite, Anthracite , Gelignite, Javelin, Fury, and Electra. . "Angelica" was almost an alias for Demona in the pilot  and then again in "Sanctuary" for her human name before settling on Dominique Destine. Variations such as "Angel", "Angelique" and even "Dierdre were considered.
Greg Weisman and Marina Sirtis both have different stories on how the latter was cast in the role. According to Weisman, Sirtis was the first actor to read for Demona and she nailed it right then and there. Marina, on the other hand claims that she had to read and audition for the role several times before it was given to her.