So D&D characters come back from the dead all the time during campaigns through use of magic, and no one really raises too much of a fuss about it. That's fine.
But if a character (and I'm more thinking of an NPC or a villain more than PC/good guys, if that matters) repeatedly extended their life through unnatural magic, wouldn't some immortal beings take notice of a soul that refused to move on? Would those beings be Gods (maybe with the grave domain), and if so, which ones and how would they deal with the situation?