Dragon

Hudson, Goliath, and Demona battle a dragon in the Gargoyles: Dark Ages pitch. [1]

The Dragon is the subject of an oath ("By the dragon,...") used by Iago, Demona, and Hudson. The exact nature of the Dragon is as yet unknown (though all of them were once members of the Wyvern Clan, and a wyvern is a two-legged dragon). ("Possession", "Tyrants", "Render Unto Caesar")

When the Commandos depart from Castle Wyvern, Hudson thinks at first that their helicopter is a dragon, before Lexington identifies it to be machine. ("Awakening: Part Two")

It is uncertain yet as to whether genuine dragons exist in the Gargoyles Universe, beyond the magically animated stone statue that King Arthur, Griff, and Macbeth battled in the Brooklyn Botanical Gardens. [2]