Undeath to Death

From HGWiki

Caster Level(s): Cleric 8 | Wizard / Sorcerer 6

Innate Level: 6

School: Necromancy

Descriptor(s): Divine

Component(s): Verbal, Somatic

Range: Medium (20 metres)

Area of Effect / Target: Large (5 metre radius)

Duration: Instantaneous

Additional Counter Spells:

Save: Will Negates

Spell Resistance: Yes

Description: This spell slays 1d4 HD worth of undead creatures per caster level (reaching 60d4 at level 60). Creatures with the fewest HD are affected first; among creatures with equal HD, those closest to the point of origin of the burst are affected first. When cast as a Cleric spell, the casters Charisma modifier will be used if it is greater than their Wisdom modifier.

Notes: The slaying is done with Divine damage equal to the target's current hit points. (Thus Divine damage resistance or immunity – rare in general, and more so for undead creatures – could save a target.)
This spell goes through walls, so it can inadvertently kill undead not yet seen by the caster.
The number of hit dice affected is actually a single roll of a d4, which is then multiplied by the caster level.