Dr. Cynthia Chalmers was a renowned archeologist who was destined to have a short career ... and life. She was diagnosed with an aggressive form of cancer. She formulated a solution and began searching through her father's papers, (against Her father's wishes, while He was in hospital) and came across Blueprints for the Mk II's and co-ordinates that gave the location of Larry Trask's inactive Mark II Sentinels. She had theorised that a cerebral transfer might be her one hope for survival.
She headed for Australia, leading an expedition following the co-ordinates to their long-abandoned base. Her work crew inadvertently awakened one of a trio of inactive Sentinels (who in turn accelerated their self-repair program) The triad (defeated by the Avengers in The Avengers #104) were leaderless and decided to reassemble their former leader Number Two, designating him Number Two-B - leaving Cynthia tethered as her traitorous work crew had left her. The quartet evacuated the Ant-Hill, taking the necessary equipment needed to continue their project to control Solar flares in a view to sterilising mankind, relocating to the Solar observatory in New South Wales.
The X-Men arrived at the Ant-Hill discovered dismembered Sentinels and the bodies of the work crew, finally coming across (a dehydrated) Cynthia Chalmers. To save time Psylocke mind-locked with Chalmers and shared the link with the other X-Men, ( Colossus, Havok, Rogue, Storm, Wolverine). The Sentinels had already abducted a mutate for experimentation, the Gamma-spawned Abomination and Doc Samson. The hibernatory Sentinels were no match for the combined forces of the mutants and the gamma-mutates. They fell in battle.
The Abomination and Number Two were lost within a crevice of the Abomination's making. The X-Men assumed they were both dead, leaving the battlefield, (exiting via a wormhole) and Cynthia at her request, within seconds the ground shook and the Abomination erupted from the earth, holding Number Two's head. Cynthia was a loose-end that the Abomination could Not leave behind, It was then that Cynthia confessed that She had already been given a death sentence. She offered Emil an alliance. They would work together to repair and make adjustments to a Sentinel from the remains of the four fallen ones, crowning it with Number Two's head. Cynthia would upload her consciousness into the Sentinel and use it to slay her "enemies", the X-Men. With her inevitable death, Emil would inherit it. Using the powerful weapon as he wished.
What she didn't count on was the Sentinel's Original programming over-riding subsequent uploads, Number Two was gradually resuming control, the X-Men returned to the fray, Psylocke made contact with and tried to help Cynthia gain dominance, But Cynthia realised She was losing, and soon the Original program and sub-routines would be in place, and the Sentinel would present a threat to Humanity again. Determined for this Not to happen, She decided to surrender her life, with her remaining vestige, she controlled the Sentinel to leave and head for the Sun, thus terminating them Both.
In human form, Cynthia had the average strength of a woman engaging in regular exercise. She was of gifted intellect, skilled as an archaeologist and had rudimentary knowledge of robotics.
Her engrams merged with a Mark II Sentinel, Cynthia had all their powers. Including superhuman strength and durability, capture features such as sleep gas, catch nets, and metal coils, x-ray visi-probes and other scanning devices, hyper-adaptability protocols enabling alteration to combat parameters as necessary to face any newly identified threat.