I received my exotic cipher, and went to Rahool to see what he had to offer, but I already owned them all. I then waited for this weekend to check out Xur's offering, but nothing special showed up in his menu. I looked online, and found that it could be used for an Exotic Engram from him. Looked again to make sure, but nope. Won't allow me to use it, only gives me the option for Legendary Shards.