Amber Storm is an assassin for Diamond Logistics.
We learn an amazingly little about this organization but from that very sparse amount we can deduce that it is a private corporation affiliated with the American government handling very sensitive operations on its behalf all to give it that all-desirable "plausible deniability".
We do learn that it is run (and likely founded) by a woman who is only known as 'Mother'. At least that is the only name that Storm refers to her as. Obviously she has a real name but whether Storm knows it or is just being circumspect is not disclosed. She is described as "an impressive, yet decidedly odd woman who wore sunglasses inside throughout".
Part of the ambiguity over the organization and its leader stems how Storm first got connected with it. "She had been at university studying when a job came up. Someone suggested she apply for it. A fellow student, Amber thought at the time, although she had no recollection of seeing this person before. Not that that was unusual in itself. University was a big place." Storm further recalls how "the job was shrouded in mystery. The insinuation was the position was top secret, with a government agency or something similar, not that anybody outright said that."
After what Storm thought a shaky interview she was nevertheless offered a trial period which naturally started with intense training. She spent more than a couple of years "retraining her mind, learning how to kill people, studying pain, both how to absorb it and how to dish it out." When she was finally given a mission, she was excited and relieved - "two years is a long time to work on theory. It was time for a little practical application."