[quote=@ZAVAZggg]
I suppose a new character will be mandated, though what kind they will be I do not know.
[/quote]

You could just roll him back a few hundred years. Make him a fresh vampire struggling with if his vampirism means the loss of his humanity, a deep seated sense of betrayal gnawing at his soul from what his brother did to him, caught between a desire to return home and exact vengeance or if home would even be a good place for him to be now that he's a monster. There's plenty of places to take a monstrous character struggling with if being a literal monster means they have to act like a monster and being tempted by how easy it would be to simply stop caring about anyone or anything but themself.

Incidentally there's nothing wrong with writing to explore a concept you find interesting but have you tried writing one you simply find enjoyable? My experience is that you get more out of writing something you are having fun with over something that feels like a chore. That doesn't mean everything always going smoothly for your character, conflict is the basis of stories, but it means making a character that excites you to write about, even if it's not particularly complicated. (You may actually find that less complicated is better because it leaves you more to explore in the roleplay itself.)