FP Problems

[Rolando]

13 uses you mean 13 energy or 13 uses, how many energy per use? normally powerstones hold energy for spell casting, a 13 powerstone allows you to use up to 13 energy from it in a single casting or multiple as you sees fit, recovering such energy slowly according to mana level.

You may want to look at the Energy Reserve advantage, or ask your GM if you can get extra fatigue (maybe with the limitation of only for spell casting). The energy reserve may be even in "objects of power" similar to powerstones but depending on how you build the energy reserve it can be more flexible, it is basically gadget energy reserve.