Warlock Utility 10Darkest Mirror
A dark membrane snaps shut over your eyes. They reflect another world now, filled with shadows and spectral foes.
Minor Action Personal
Effect: Until the end of the encounter, you can see invisible creatures as if they were not invisible. All other creatures, including your allies, are invisible to you. You can end this effect as a minor action.
Published in Forgotten Realms Player's Guide, page(s) 38.