Morpheus is a somewhat major villain in Fallout 1. He is the leader of the cult known as the Children of the Cathedral, which is a front used by the Master to recruit people to turn into Super Mutants. Morpheus was one of the first humans recruited to the Master's cause, and his job is to indoctrinate initiates and make sure they stay loyal. He resides in the cult's Cathedral, on the highest floor. He holds an item which gives access to the Master's secret vault beneath the Cathedral. Morpheus was once a member of a gang of Raiders known as the "Rippers", who were actually supposed to be in the game but were cut. Morpheus is either killed by the player directly or presumed dead if the Master's Cathedral is blown up. You can even trick him into escorting you to the Master.
Fallout: New Vegas