|DC/Marvel: Age of Infinite Heroes|
Sage is a mutant. Aside from her name, Tessa Niles, nothing else is known of this secretive woman publicly.
Within the X-Men however, she is a known mutant telepath with a computer-like mind, capable of infinite recall. She is however a long-time ally of Professor X and was found to have acted as his mole inside the Hellfire Club. Her name, is likely an assumed one.
- Tessa lives in a harem in the Balkan region of Europe. In her teenage years the Russians invade Afghanistan so she has to learn how to use weapons and fight against soldiers and local bandits. One day, she feels compelled to enter a local cave and finds Professor Charles Xavier trapped under some rocks, his legs crushed. Soon after, some bandits who had raped and killed a convoy of U.N. workers attack them, but Tessa drives them off killing most of them. The more time she spends in guerilla warfare the more of an expert she becomes, her mutant powers kicking in and allowing Tessa to rapidly learn anything she needs from the people around her.
- Professor X recruits her into the X-Men but keeps her secret so he can use Tessa's telepathic power and skills to spy for him. The first place she goes to, however, is the Hellfire Club, something Tessa accepts gladly. Then codenamed Sage she becomes Sebastian Shaws adviser, hoping the man won't be corrupted by power and remain true to his ideals of fighting for mutants.
- In the Hellfire Club the limits of Tessa's sanity are tested by virtually every member. She witnesses Emma killing off another applicant for the stripping job on the spot, she is there numerous times as both aide and victim of Selene's tortures, Leland's excessive tastes and Pierce's sadistic plotting. Sage endures, however, hoping Shaw will remain true and control the others. In the end he does not, and Tessa finds herself alone with monsters, and she is forced to pretend to be one of them.
- Later, Shaw makes a poker bet with billionaire Elias Bogan where if Shaw lost, he will have to hand over Emma Frost, now White Queen, and if Bogan lost Shaw will receive his entire fortune. Bogan had never lost a game before, but astonishingly, Shaw wins, mainly due to Tessa's help.
- During the White Queen's plot to take a hold of Jean Grey and use her as the new Black Queen of the Hellfire Club Tessa is the subtle instrument through which the X-Men manage to get to Jean fast enough to avoid any additional damage to the telepath. Still, Sage is too late, as the Dark Phoenix still emerges from the tampering with Jean's mind.
- When the strange, otherwordly invaders come to Earth, Sage concentrates on working small groups of survivors under the New York streets, using her espionage tactics to give the invaders problems while trying to figure out what to do. Sage is responsible for keeping a anonymous communication network between the forces of Earth while they fight the invaders. After the Crisis is solved Sage goes back to Hellfire to discover a completely changed world, one that Sebastian Shaw readily explores with his secretary.
- Her parting with Hellfire comes when Bogan, knowing that Tessa was the one responsible for Shaw's win at the poker game, captures Tessa and horribly tortures her, both in body and mind, scarring the woman beneath the eyes so she never forgets him or what he did. Sebastian Shaw can pay the ransom but opts not to do it. He abandons Tessa.
- Abandoned by Shaw, Tessa is saved by Peter Wisdom, and together they found X-Factor Investigations. Sage nullifies her telepathic abilities to prevent Bogan from finding her ever again.
Selfless: What made Sage help freedom fighters in the both the Middle East and the Balkans when she could have just turned her back and run, what made her infiltrate the Hellfire Club and interact with the likes of Donald Pierce, Selene Gallio and Emma Frost. Whoever she is, Tessa Niles is selfless, she is willing to go far, very, very far to make sure the needs and wishes of others are met despite her own. In this case, Xavier's Dream is one of the things she treasures the most.
Believer: Before meeting Charles Xavier in a cave the slave Sage was belonged to a warlord of the Balkans. Despite her selfless nature, she lacked the motivation, that spark to make the best of what she was. And Professor X gave it to her, showing Tessa Niles a world that was beautiful and, to most, utopic. Maybe it's her last ditch of innocence, but Sage believes this, and losing this faith could change her forever. It is a dream worth fighting and dying for.
Driven: When Sage sets a goal to herself, there is no way she is quitting, no matter how dark the road no matter how hard the bludgeon. Tessa is almost machine-like in her commitment to the objective.
Pragmatic: Sage is an expert in dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations. She will use her knowledge to asses a situation to the smallest detail, but in the end, she will do the sensible thing, unless it is against what she believes to be right. The flip-side is that for Sage there are very few things about herself she is not willing to sacrifice to see her objectives completed.
Tormented: The gruesome torture Elias Bogan has inflicted upon Sage is enough to completely keep her awake some nights, and the mere sound of his voice could paralyze her. Elias Bogan is the demon to Tessa, but he is not alone in her nightmares, as the whole Inner Circle was cruel enough to give her plenty of memories to relieve in her perfect memory.