Ly'lac as a hero of Doom is perfect. Sorry to say I don't really think Tavvy is Doom. I think BKEW on tumblr (or maybe someone in their ask box? Don't remember) was likely spot on in speculating that the colors on page https://beyondcanon.com/story/214 signify those kids' aspects, which would place Tavvy as a Breath player. I think it actually makes a lot of sense for him. His chumhandle suggests he's a gymnast, and that involves a lot of flying about in a controlled manner. Not that chumhandles often signify classpects like that, I just think it works in this case.