Grey Man

The Grey Man was a member of the universe's first species. They imposed the concept of duality ("good" versus "evil", "us" versus "them") on the universe. The Grey Man created Cathedral, a metacultural engine to introduce uncertainty to that duality. His people considered this blasphemy and exiled him. But since he used his own energy to create Cathedral, as long as it existed so did he. Cathedral was ruled by the Mandelbrot Set, a set of stone heads that were in the Cruakh. He summoned the Seventh Doctor to stop Gabriel and Tanith. When Cathedral was destroyed, it continued its existence with the Grey Man's form and identity. (PROSE: Falls the Shadow)

The Grey Man was one of the guests at Benny and Jason's wedding in Cheldon Bonniface. (PROSE: Happy Endings)