SRD:Mass Inflict Critical Wounds

Negative energy spreads out in all directions from the point of origin, dealing 4d8 points of damage +1 point per caster level (maximum +40) to nearby living enemies.

Like other inflict spells, mass inflict critical wounds cures undead in its area rather than damaging them. A cleric capable of spontaneously casting inflict spells can also spontaneously cast mass inflict spells.