In a games like Mage the Awakening you can have a power that isn't exactly a delimited power from a list. That is, the power has a general constraint based on the fiction and some theme and your level of power, and may even have a constraint, but within that the effect isn't a specific power or spell.
For example, you might have access to the Death Sphere of magic, so you can make effects proportionate with your power level and they have to involve Death (decay, etc) but it's something you can kind of make up on the fly. And there's a risk, the weirder and more powerful the effect the more likely it is it will blow back on you.
Is there a way to simulate that in Revolution D100