Full Name: Tessa (Niles?)Sage was a young soldier in Afghanistan when she encountered the newly-crippled Charles Xavier just after his battle with Lucifer. She also apparently met Sebastian Shaw there as well, and saved both their lives, though the details of Shaw's rescue are still unknown. Xavier identified her as a mutant, and she returned to the United States to train with him. However, Sage did not join Xavier's students as X-Men, but instead was sent to work for Shaw and spy on him for Xavier.
As Shaw's familiar, Tessa advised and counseled her employer in business as well as in his more shadier dealings. She warned him about accepting Selene as Black Queen, a move which eventually proved costly to Shaw and the Club. Once, Tessa aided Shaw in defeating an emissary of telepath Elias Bogan in a card game, and Bogan later abducted Tessa in retaliation. Much later, Bogan tortured Tessa and gave her scars or tattoos on her cheeks, which she usually hides telepathically. Shaw refused to pay Sage's ransom, but Xavier sent Storm to save her. Tessa then left Shaw's side and returned to the X-Mansion, revealing Professor X's orders and her spying on and controlling of Shaw to the X-Men. She became an advisor to the X-Men, and was helping to train some of them. Tessa also made an attempt to persuade Senator Kelly not to run for President on an anti-mutant platform, saying that by doing so he became no better than Magneto, who he felt was opressing the human race and threatening it with genocide.
Shortly thereafter, Storm renamed Tessa as "Sage" and took her and a number of X-Men to find the lost journals of Destiny. Sage developed incredibly complex cyber-sunglasses for the team that functioned as web browsers, communications links and much more, and used them to keep the team linked as she provided them with invaluable data. When Beast was severely wounded by Vargas in battle, Sage used her catalyst ability to jump-start his mutation, hoping that his healing factor would accelerate. Unbeknownst to either of them, Sage's actions caused Beast to mutate into a more leonine form. Sage later jump-started Davis Cameron's latent abilities during an alien invasion, giving him his Slipstream powers. During an alien invasion, Rogue also asked Sage to affect her powers, which were out of control since she absorbed Z'Cann the Skrull's abilities months before. Sage's catalyzation gave Rogue the capability to control her powers and call upon any power she had ever absorbed, and to use multiple powers at once. Afterwards, Sage teamed with Bishop in a detective capacity, first to investigate the accused murderer Jeffrey Garret, and then to discover who shot Emma Frost.
Sage and the X-Men eventually defeated Bogan, and Sage returned to the X-Mansion and worked with Storm's X.S.E. team. During a battle with the Fury, the mutant-killing robot used Sage's cyberlink glasses to backtrack the link and co-opt her mind, causing her eyes to shift to mimic the Fury's. However, Sage fought off the Fury's influence and helped the team destroy it, catalyzing the X-Men's powers to allow Marvel Girl III to create a miniature black hole. Next Viper put the X-Men through the London Murderworld, all to target Sage, who had injured her in Madripoor. Viper was able to immobilize the entire team, and shot Sage in the head at point-blank range. Except that it wasn't Sage: it was Wolverine and an image inducer.
Shortly thereafter, Sage received an invitation from Shaw to rejoin the Hellfire Club, and she appeared to accept, but didn't tell any of her teammates. The X-Men followed her to the old Club, where they were attacked by Sage and secretly, by Selene. However, Sage's attack was a ruse, and she sent Emma and Marvel Girl III to Hong Kong to bust up a slaver ring, while she sent the other X-Men to Paris to stop Donald Pierce from taking over the Hellfire Club. Sage made Shaw think that she was backing him, but she didn't warn him about Pierce, and Shaw, though he beat Pierce, was wounded and unable to take control of the Club, which devolved to Roberto DaCosta (Sunspot), who seems to be Sage's primary choice for the position of Lord Imperial. Sage left the X-Men to advise Bobby on his new role.
After M-Day, however, Sage was in Britain when some X-Men arrived after hearing of Dazzler's death. She ended up joining the New Excalibur team, and used her cyberpathic skills to help monitor and advise their strategic moves. Pete Wisdom found her attractive, but she consistently rebuffed his advances. When the rogue Captain Britain named Albion attacked Excalibur, Sage found only limited information about him, so she dyed her hair blonde and took the alias Diana Fox to infiltrate Albion's team of rogue "Sword" Captains. She was given a sword and a costume, and only her telepathic skills saved her mind from being corrupted, and so she gained his trust. However, she failed to stop Albion from casting a spell that stopped all technology in England. Then, when Excalibur and the Shadow-X-Men tried to stop Albion, "Diana" decapitated Shadow Cyclops with her sword, possibly due to the sword's influence, and Albion gave her the codename Britannia...
224