Shyft was one of several children who was kidnapped by rogue scientists and relentlessly experimented on. In her case she gained the power to shapeshift into an exact copy of anyone one she senses their life force for a few seconds. She perfectly copies their appearance, powers and durability!
After they grew up and their powers become beyond what their captors could handle, Shyft and the others test subjects murdered all of the scientists and escaped back into the outside world, but they vowed to never harm any innocents.