Editing DS Manual (section)

=== Power (PWR) ===
These points act like a reservoir that you can tap for power, but are also a determining factor in not only how many Magic Spells you can cast, the amount of times you can activate a Wondrous Feat, and also how powerful they are. Additionally, this is the only stat point that can reduce to zero. In lieu of PWR, a character can use END to exhibit feats of power but in much smaller doses.