Lord Nixus is a powerful dark wizard (Who has some other unknown blood mixed in)
And yes, but within reason. Your character can change into/be (depending on the monster you choose) anything. So vampire, werewolf, gorgon, harpy, satyr, demon (there is different kinds of demons so you will have to specific) , etc.
You can't be anything super big or powerful like a dragon or anything like that. Also each monster has weaknesses that can/will be exploited. So no one is playing a god like being