Death Grimace

Necromancy [Evil]
Level: Asn 1, Blk 1, Sor/Wiz 1
Components: S
Casting Time: 1 action
Range: Touch
Target: One corpse
Duration: Permanent
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.