So today I was pondering a My Little Pony: Friendship is Magic version of Lucian. I figured he could be one of two things, either a Gryphon like Gilda, or a young Lugia, sort of like how Spike is a young dragon. Size wise, he's big, but not too big. I'd estimate he's a little taller than any of the Mane 6. If he were roosting, he'd be eye to eye with them, so I guess his size is sort of in between characters like Twilight and Celestia.

Alt: http://www.furaffinity.net/view/7011082/