Mythological creatures are cool, as long as they are [i]original[/i] mythological creatures. With that in mind, mythological creatures, like our characters, are (oh my god i'm going to have to type that word again) [b]mythological[/b]. So they are either going to have to be extremely rare or previously extinct alongside our characters, who find a way to (or have one come back alongside them) bring one or two back for our purposes. 

And, of course, it will be a democracy for approval with NPC fauna. 

EDIT: reading characters so far, give me some time and i'll start approving / giving feedback for WIPs.

EDIT: Raven, Altim is naturally accepted. Welcome aboard!