Seb

Seb was an AI interface (TV: Death in Heaven) who worked for in what he liked to call the Nethersphere. He welcomed Matthew, a Shoreditch policeman who was killed by a Skovox Blitzer, as Missy was busy at that time. (TV: The Caretaker)

He also welcomed Danny Pink to the Nethersphere. He offered the man coffee and asked if he had arranged to be cremated. Seb told Danny that he had died, and that he could still feel his body, even though his consciousness was no longer a part of it. He also arranged a meeting between Danny and a boy he had once killed while on duty. When the boy fled during the meeting, Seb told Danny to allow him to leave.

Seb allowed Danny to talk to Clara Oswald, after the latter had, quite "rarely" in his opinion, managed to call Danny. He watched as the two talked, and Danny broke down after Clara ended the call. Seb then gave him the chance to delete his emotions, leaving him alone to make the decision. (TV: Dark Water)

He was in the Nethersphere with Danny and the boy he killed stating that now the dead were going back home as all the lights in the Nethersphere turned off. After that, he appeared in the Nethersphere with Missy watching the Twelfth Doctor and the TARDIS free falling from a plane. He showed clear signs of being impressed when the Doctor managed to open the TARDIS, and keeps on contemplating the Doctor. Missy becomes visibly annoyed with Seb, and she casually killed him with her weapon. (TV: Death in Heaven)