A corpse within range swells up and becomes bloated with magical energy, which fades away once the corpse is bloated. If touched, pierced, or hit, or when the caster uses a bonus action, the corpse ruptures and explodes, splattering blood, gore, and internal organs all over everywhere in a 20 feet sphere.
Creatures hit by the explosion must make a Constitution saving throw or take 3d6 poison and 2d6 necrotic damage, or half on a successful save. A failed save also results in the creature being sickened and thus is incapacitated for the next round.
The bloated corpse is non magical. If the corpse is animated into undead, it explodes when hitting 0 hit points, taking more than 8 piercing or slashing damage or if the caster activates it using a bonus action, and then the undead dies.