>Why does this spell affect corporeal undead, and not affect incorporeal undead? I guess what I'm asking is, what is the fundamental connection between a physical presence and this mystical 'life energy'?<

The technical OOC reason is mostly because that's Holy mana domain.

The technical IC reason is because the spell works by overloading the life energy in something to cause the physical body to warp, and the spell can't grab on to the intangible nature of non-corp critters.

-Z