Hammerhead said:
Maybe a Quickened Unholy Blight?
This is one good option as I agree that standard Unholy Blight at will is kind of weak. Another option is to replace Blasphemy with another 7th level spell from the Book of Vile Darkness. I happen to have it here, so here are some possibilities:
7th level spells
BESTOW GREATER CURSE [Transumtation]
Touch, Permanent, Will Negates, One ability score is reduced to 1
WRETCHED BLIGHT [Evocation, Evil]
Medium range (20 ft burst), Fort Partial, 1d8/level (non-evil only) [15d8 max] + 1d4 rounds of stun [Successful Fort save reduces damage by half and negates stunning]
RAPTURE OF RAPTURE [Conjuration, Corrupt]
Touch (can touch up to 1 living creature/level in consecutive rounds), Fort Half, 6d6 damage, 1 rnd stun, 1d6/rnd until healing spell is cast
Wretched Blight 1/day seems about right. Grimm won't be affected but it should stun a good percentage of the party and put them in some serious hurt.