Nightingale Subterfuge is a skill awarded to the player by Nocturnal in the final Thieves Guild quest Darkness Returns. Stepping on the Half Moon platform confers this skill. The skill is listed under Powers.
People and creatures in the spell's area of effect will attack anyone nearby for 30 seconds. Powers can only be used once a day.
Subterfuge is a very powerful ability, and compares favorably to analog illusion spells. It affects NPCs who are too powerful for Illusions Expert frenzy spell Rout — which even after all perks and vampiric 25% boost reaches level 32. Subterfuge will affect most NPCs in the game.
A good strategy is using this in an area where there are multiple enemies at one time. While hidden, use the Throw Voice and use the subterfuge when they are in one area. You will then see them tear each other apart which is very amusing to people who like seeing people being manipulated into attacking their allies.