At the beginning of World War II, Leo and Una shared the running of "Into the Mystic" with Griff. When the Battle of Britain began, Griff felt it his duty to help defend London from the Germans, but Leo and Una viewed the war as a "human problem", and chose to simply continue running the shop and let the humans fight the war. When Goliath arrived in 1940 via the Phoenix Gate, he chose to join with Griff, and accompanied him on his last engagement in the Battle of Britain, before both vanished (due to Goliath’s taking Griff forward in time to 1995).
Leo and Una believed that Griff had been killed in the fighting, and blamed Goliath for it - partly because of buried guilt; they knew, deep down inside, that they should have helped protect London alongside Griff. In the over fifty years that followed, during which time they became mates, they continued to view the shop alone as their protectorate, turning a blind eye to the street crime in their neighborhood, which they viewed as somebody else’s problem.
When Goliath and his companions arrived in London on the Avalon World Tour, Leo and Una angrily accused him of being responsible for Griff, and sought revenge by capturing Elisa, Angela, and Bronx and chaining them up in the shop’s basement. Goliath realized that the only way that he could save his friends was by going back in time to 1940 to discover what had happened to Griff, and used the Phoenix Gate to return there.
After his departure, Leo realized, and convinced Una of this as well, that the real reason for their anger was their buried guilt, and freed Goliath’s companions. When Goliath returned with Griff to 1995, Leo and Una forgave him, and afterwards expanded their protectorate to cover London rather than just the shop, protecting the innocent from those who would prey upon them.
Leo looks very much like a winged lion; hence his name.
Voice Actor: Gregg Berger