Religion: not determined yet
Alter Ego: Tessa Hartley
Other Names: Tessa Niles; Lady Tessa; "Diana Fox"; Britannia
First Appearance (additional details): (as Tessa) The Uncanny X-Men (vol. 1) #132 (Apr. 1980): "And Hellfire is Their Name!"; (as Sage) X-Men (vol. 2) #109
Number of appearances: 238
Worked for: Sebastian Shaw
It is certain almost that "Tessa" is a pseudonym. The real birth name of the former Hellfire Club associate known as "Tessa" (who became known as the X-Man named "Sage") is, as yet, unrevealed.
This character is in the following 64 stories which have been indexed by this website:
Classic X-Men #6 (Feb. 1987): "Merry Christmas, X-Men... (supplement)"
Marvel Knights Spider-Man #6 (Nov. 2004): "Venomous: Part Two" (1-panel cameo)
Marvel Universe: The End #1 (May 2003): "Predestination"
Suggested links for further research about this character: