You attempt to trap an incorporeal undead within your own body. If you know the undead creature’s birth name, the spell has unlimited range and the undead suffers a -2 penalty on its saving throws. Otherwise, you must be able to see the creature, and the spell is countered if the undead is protected by protection from good or a similar effect. Voice of the grave can be combined with magic circle against evil and similar spells as if it were a calling spell. Doing so extends voice of the grave’s duration so long as the undead does not break free of the circle.