Creator
Bill Sienkiewicz, Chris Claremont
Chris Claremont, Paul Smith
In Comics
New Mutants #25 (March, 1985)
The Uncanny X-Men #169 - Catacombs
Base
formerly Ruth Aldines mind, Utopia, San Francisco Bay, California; Westcliffe, Colorado; "No-Time"; Moira MacTaggarts Mutant Research Center, Muir Island, off the coast of Scotland; Haifa; Paris, France
The Xavier Institute, Salem Center, Westchester County, New York State, (former) The Alley (beneath Manhattans surface), X-Factor Is sentient starship