Devil Descendants

The Devil has left a mark on the world, at random, one devil boy is born, completely indistinguishable with every other human, the person were to live like a human for the first years, when he reaches the age of 16, the suited devil comes to him. For example one boy would turn 16, a devil would possess him, he still has control over himself, but the devil's ability is given to him, one devil may have a steel skin ability, while another would have super strength and so on. When the devil boy turns 16, he suddenly becomes attuned to the weapon that the possesing demon wields, one may wield an axe, another may wield a spear and so on.

Ups-
-Abilities can vary, no limit to it
-Are , can live for eternity, but can still be killed
-They're resistant to fire and dark magic, all devils can see through the dark

Downs-
-Are terribly weak against light magic
-Sometimes the random ability chosen isn't good at all
-most devils have terribly low defense