Well, there's the classic 1976 movie of The Omen, and especially "Damien Omen II" where most of his canon I pulled from. There's also Omen II of his future, so this one is at a point when he's.. sorta got "evil" type tendencies at times, but not really at the point yet of being full-on crazy evil. And other sides to him, I included a bit from my headcanon and writing style of him, from some of the impressions and stuff from the Damien TV series. This also covers a lot of his history in the films too.
Which is only one season, and some parts of it really drag on a bit. But it's something to watch just to complete the series.