Revenge's Eye 2014
2nd-level divination
You touch a creature's visual organs and grant them the ability to see the trail left by creatures damaged by a weapon you cast invisible creatures; it only reveals trails left by those affected by order of revenge also cast by the spellcaster.
At higher levels
When you cast this spell using a spell slot of 3rd level or higher, you can target +1 creature for each slot level above second.
Source: Warlock Zine (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details