D&Dtools1

You tear off a piece of a creature's life force, corrupt it with negative energy and the power of undeath, then bind it to its body to allow a blasphemous transformation should the creature later die.
The subject of this spell loses 2 points of Constitution.
When the subject dies, the corrupted life force begins a slow change in its body, causing it to animate as a crypt spawn at the next sunset (see the crypt spawn template in Chapter 7).
If its remains are destroyed, the undeath after death spell cannot bring it back as an undead.
If the spell is dispelled before the subject dies, it does not regain its 2 lost Constitution points.
Material Components: A piece of obsidian shaped like a heart, which is placed on the subject's chest, and a black onyx gem worth at least 50 gp per HD of the subject creature at the time the spell is cast, which is placed in the subject's mouth.