The Fellowship was an organisation that worshiped evil. Trying to summon the Yssgaroth to them on Earth in 1888, they were responsible for the Jack the Ripper murders.
The Seventh Doctor burned down their meeting place, but the group survived. The archaeologist Roberts was a member during the later part of the 20th century. It existed at least another 400 years, as Jarak and Ell were also members. Jarak was killed on the seventh planet of the Althosian system in 2400 by time-stopping red weed. Ell was killed later by an explosion in an ancient castle on the same planet as she awaited the return of the Yssgaroth. (PROSE: The Pit)