At-will, std, ranged, 2 Mana; targeted corpse or corporeal undead creature explodes. The creature suffers heavy internal damage (Con half, if not a corpse), and the same damage explodes in a burst 3 of explosive damage.
If the explosion hits another corpse or corporeal undead, it triggers another Corpse Explosion on that target. This secondary explosion inflicts half the damage of the explosion that triggered it, and cannot in turn trigger tertiary explosions.
If the target is an undead minion under your control, you may direct it to fail the saving throw if you desire.