Curse Of Despair

Warlock Invocation
Level:Least, 4th lv.
Components: V, S
Casting Time: 1 standard action
Range: Self
Duration: Instantaneous
Saving Throw: Yes
Spell Resistance: Yes

You can use this invocation to bestow a curse upon a touched opponent (as bestow curse). Even if the save against this ability succeeds, the creature takes a –1 penalty on attack rolls for 1 minute.

(Complete Arcane, Page 132)