[Baalz]

Power of the Spheres is actually the effect that the Crystal Shield gives (casting PotS on somebody holding the Crystal Shield has no effect), so it only effects mage/priests.

To give some context of what I'm thinking about LA C'tis has a pretty cool H4 spell to buff all their undead, the H3 version only hits 5 squares, which is ineffective given the large amount of undead you're fielding. It seems like the only way to get a H4 priest before late game is to make a Lizard King your prophet...which obviously is limited to one at a time. Crystal shield, PotS, communion, hell power, and (presumably) Crystal matrix won't work on priests...