I think it'd be entertaining as a quest mechanic to have a boss with a soul stone in a quest at some point. Just to poke a little fun at the whole "soul stone" mechanic. Basically how the quest would work is:
1. You'd have to beat up the boss to get their soul stone.
2. You'd have to carry their stone to the end of the quest as a quest objective.
3. Any time you get near a shrine, the boss would rez, and you'd have to do it again.
4. If you wanted to get REALLY silly, the boss would refuse to rez at the end, so you'd have to let yourself be killed and beat them up in the Plane of Dolurrh to force them to rez.
5. Maybe have an option where you could blow up the shrines to prevent the boss from rezzing.
The more inane death-related goofiness, the better, IMO.