Death Grimace(Book of Vile Darkness)
Level: Assassin 1, Blackguard 1, Sorcerer 1, Wizard 1,
Casting Time: 1 action
Target: One corpse
Saving Throw: None
Spell Resistance: No
The caster marks a corpse with a particular magical "signature", thus identifying himself (truthfully or falsely) as the murderer.
Some assassins use this signature as a sort of calling card, while others use it as a way to prove that they earned their pay.
The signature can take many forms: a specific expression on the face of the corpse (hence the name of the spell), an actual rune, a word written on the corpse's flesh, a discoloration of one eye, and so on.