Subject-006X is actually a clone made by the "Life Foundation" as one of their first genetic experiments, the original organism chosen for the test was Calvin Rankin better known as The Mimic. The goal was to bond the mutant abilities of mimic with an artificial made gland that secretes a kind of X-gene in a richier state than those found in mutants.
Eventually Subject-006X escaped the lab facility, the scientist erased most of hes memories expect for a brief flash of the original Mimic's life. So after some days hidding in the underground parts of New York, he started realizing he could "sense" others mutants powers, and not only that, he could copy them, of course, it was for a brief time since he didnt have full control of hes powers, nor how to keep those copied abilities.
From time to time, the mental block was weakening giving Erick Rayn (the name he choosed for hymself)new images of hes "past life" confusing him even more and more, and eventually exausting him to the point he fainted in the middle of the sidewalk. He was then found by Dc. Agatha Rivers laying there, she took him to "Second Chance" a hospital for street kids that were greatly injured or with desease. Touched with Agatha kindness, he decided to help the doctor in whatever needs the hospital had, except to the fact that, they didnt have much money to mantain "Second Chance" open.
He decided then to do what a desesperated man would do in that situation. He went one night in hopes to steal a bank and pay the bills that were eating the Hospital. There he found a gang of mutants that had the same "need of urgent cash". More interested to steal the money for HIM rather than doing the hero role, he defeated the gang using theire own powers. For the first time, he felt good with hes abilities. He eventually copied and Evolved to Ultimate level the power of Colossus, the fire manipulation of Phyro, Spiderman, the healing factor of Wolverine and Nightcrawler's teleport.