[@Keksalot] Well, I can't say I know much about Cossack history, but if you can keep it reasonably accurate, then I don't see why you couldn't play as a significant military leader from that time period. As far as Daywalking goes, however, I'm going to say "no" to other alterations along those lines - becoming a Daywalker is specifically a counter to a common vampiric weakness, whereas "drinking warlock blood to gain the ability to use magic" has no particular basis in, well, any media I know of.