And one mentions how strains of disease mutate.
Hmmm. Should it do that? Mutate to produce new powers?
Nah. I want random. Strains would put too much pattern into it. I could work with that except that power-seekers (a rather precise term in this world) would exploit it in their quests to gain powers without accidentally throwing themselves into a state where powers are no longer possible (or possibly they get them, and they are too obscure to use, or even identify).
Probably going to have a character talk about how they SEEM to clump -- basic statistics there.