Sebastian was introduced in B5 S2, E21, Comes the Inquisitor, after being summoned by Kosh to make sure Delann is acting for the right reasons; she is also warned this test will place her life in danger.
The man introduces himself as Sebastian, and he did live in London in the late 19th century until the Vorlons took him in and showed him things that made him the way he is now. He has been brought out of stasis by the Vorlons so he can perform a test uniquely suited to him. He then demands to get to work.
At the end of the episode it is revealed that Sebastian is
actually Jack the Ripper, drafted into service by the Vorlons, and kept in stasis when he’s not needed.
What happened to Sebastian, and those non-Vorlon wards in their custody after the events of the show? Specifically after
the Vorlons left the Galaxy at the end of the Shadow War in S4 E6, Into the Fire? Was he brought with the Vorlons beyond the Galaxy? Did the humans and Minbari who finally were able to enter Vorlons space in the year 1,002,261, find a stasis pod with Sebastian suspended inside?
What is his ultimate fate?