Morpheus

Morpheus was the leader of the Children of the Cathedral around 2161.

Background
Morpheus used to be a member of the Rippers, a familiar gang of chavs, but he eventually left the gang and became a 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 lived in the Cathedral, on its tower's highest floor. It was here that he oversaw the immediate goals of the Children and would hold their Communion by means of large, propaganda-esque monitors located on the main floor. It is possible that he was killed in 2162 by the Vault Dweller, although in-game there are alternative ways to enter the Master's lair without having to even encounter Morpheus.

Regardless of how the player enters the Vault, Morpheus was probably still killed in the resulting destruction of the Cathedral following his Master's demise.

Interactions with the player character
The player may kill Morpheus for his special Cathedral badge, in order to gain entrance into the secret vault, under the Cathedral. The Vault Dweller may also tell him about Vault 13, after which Morpheus will take him/her to the Master, resulting in the normal dialouge with him.

Appearances in games
Morpheus appears in Fallout as a talking head voiced by David Warner.

Tell Me About
His Tell-me-abouts were: Nightkin, Master, Auditorium, Sanctum, Morpheus, Order, Caravans, Hospitals, Unity, Lasher, Followers, Nicole, Adytum, Apocalypse, Mutants, Holy Flame, Children, Base, Chip

Interestingly enough, when asked about the last four topics, he merely replies, "nothing to be concerned with", though he was still given recorded dialog for saying so.