D&Dtools1

You cause the cyst of a subject already harboring a necrotic cyst (see spell of the same name) to pulse and swell.
This agitation of the necrotic cyst tears living tissue and expands the size of the cyst, dealing massive internal damage to the subject.
The subject takes 1d6 points of damage per level (maximum 10d6), and half the damage is considered vile damage (introduced in Book of Vile Darkness) because the cyst expands to envelop the newly necrotized tissue.
The cyst is reduced to its original size when the vile damage is healed.
Vile damage can only be healed by magic cast within the area of a consecrate or hallow spell (or an area naturally consecrated or hallowed).
Points of vile damage represent such an evil violation to a character's body or soul that only in a holy place, with holy magic, can the damage be repaired.
Focus: Caster must possess a mother cyst (see page 28).