Leon disappeared years ago on one of his apparently fruitless quests to the dark continent Asgard. It is later revealed that Leon is actually Allen and Celena's lost father.

Allen holds a grudge against his father because he believes that he abandoned their family. Leon met Hitomi Kanzaki's grandmother a long time ago in a pillar of light. He was killed by soldiers before he was able to return home to his family after completing his research. He's a very brilliant man and Dryden Fassa admires his work.