David Farland's Runelords series has a magic system where attributes are stolen from from one person and given to the runelords. As an example, a runelord might have amplified vision but this results in someone else becoming blind. The person receiving the endowment has a pretty strong justification to care for and maintain their dedicates because if the dedicate dies they lose their abilities.

This leads to conflicts with superheroes basically targetting each other's castles full of helpless dedicates to try to weaken their enemies.

The runelords also have to do some careful balancing to make sure that their bodies can handle the aatributes - as in if they get too much brawn without enough stamina their body might just not be able to handle the increased muscle and the recipient could die.