[quote=Stefan0620]
Are there any sort of npc creatures that could exist, that we won't be able to play as? Something like the Windingo comes to mind, for me.
[/quote]

Possibly so, but significantly less likely. The only creatures we will be likely to run into are ones derived from humans and who remain largely human; inhuman creatures or ones that formerly were but can't blend in are much less common. Much of the game will be encountering humans as well as other former humans.