(insert monster name here)'s Favorite Flavor

No save, no ill effects. The PCs reek of the scent of a given monster's favorite food. The scent may or may not be detectable to the PCs.

The monster in question now has "Life Sense" (Libre Mortis, 3.5) for 1000 feet for the PC(s) doused. Essentially the monster in questions knows exactly where the PC(s) no matter what is between them.

"Here kitty kitty" - Kobold baitmaster