Outwardly, Morpheus is the supreme leader of the Children of the Cathedral. Though he adopts a pious demeanor and can sound a bit like an old-time country preacher, he does not believe that the Holy Flame, the Dark Lord, the Master is, in fact, a god. Morpheus is intelligent, crafty, sly, greasy, and thoroughly evil. Ensnared by the promise of power rather than by belief, he has a short fuse and terrible anger, which makes him an extremely dangerous individual.[Non-canon 1]
Morpheus used to be a member of the Rippers but he eventually left the gang and became the leader of a doomsday cult. In 2151, he was found by the Master's spies and pledged his followers to him, forming the future core of the Children.
Morpheus lives in the Cathedral, on the tower's highest floor. It is here that he oversees the immediate goals of the Children and holds their Communion by means of large, propaganda-esque monitors located on the main floor. He dies in 2162 by the Vault Dweller's hand, either in person or as the Cathedral is destroyed.
Pestering him causes him to say “You were warned. Guards!” in a float complete with voice acting. He and Nicole are the only two characters in the game where this happens.
It is usually impossible to approach Morpheus normally for conversation because the nearby nightkin automatically turns hostile if the player has any companion with them (including Dogmeat), which, by extension, also makes Morpheus hostile. Even with a COC badge and robes, they will be attacked by the nightkin immediately.
Combat can be bypassed if one has a Stealth Boy, a high enough Sneak skill, and a high enough Intelligence, although if one just stands there, another nightkin will move closer and see the Vault Dweller.
Lasher can be convinced about needing to see Morpheus. If the Vault Dweller tells Morpheus that Lasher sent him up, there is a skill check. If failed, Morpheus will attack out of suspicion. If passed, Morpheus allows the Vault Dweller to leave and says that Lasher likes to get Children into trouble.
"Ahh...So you are the Vault Dweller I've been hearing about. Surprised? I have my sources. Now, I will take you as a gift to the Master. He'll be very pleased."