"I can do this!", Abadall grunted, eyes closed, brow furrowed.
"I... I think I've got it..."
Each level attained increases the instability, and thus the risk of Cascading. Whenever the character fumbles while utilizing one of their powers, a Cascade check is made. There is a percentage chance equal to the character's level x5 that they will spontaneously mutate, and slide one level closer towards total genetic breakdown. Note that this check is performed again each time they fail, making it possible (although unlikely) for a character to slide from Level One all the way to Level Ten as a result of a single fumble.