D&Dtools1

You cause the cyst of a subject already harboring a necrotic cyst (see spell of the same name) to explosively enlarge itself at the expense of the subject's body tissue.
If the subject succeeds on her saving throw, she takes 1d6 points of damage per level (maximum 15d6), and half the damage is considered vile damage (see necrotic bloat).
The subject's cyst-derived saving throw penalty against effects from the school of necromancy applies.
If the subject fails her saving throw, the cyst expands beyond control, killing the subject.
On the round following the subject's death, the cyst exits the flesh of the slain subject as a free-willed undead called a skulking cyst (see page 120).
The skulking cyst is formed fromthe naked organs of the subject (usually the intestines, but also including a mass of blood vessels, the odd bone or two, and sometimes even half the lolling head).
Focus: Caster must possess a mother cyst (see page 28).