Red Mirror is a pamphlet for making Nemesis Operatives, enemies that are duplicates of player characters with some changes. It's awesome, and I'm not just saying this because I'm credited for helping with it. The Nemeses are designed counter the character they are a duplicate of, making them a great way to up the stakes or just mess with characters that have become overconfident. Not only are they great mechanically, Red Mirror also makes them exciting narratively. There's also some very fun traits for if the players don't get killed by their reflection. The trifold layout is very neat and readable, and the art is used well.
Red Mirror can be used in any campaign or game, so I'd say- Give it a try!