Assassin
Assassin was a hired assassin of sorts, originating on the world of Water. Water was, for a time, besieged by the second branch of the Infinity Corporation. Assassin, as he refers to himself, came to Gaera Main in the hopes of gathering support and reinforcements against this threat. He found, however, that by the time he had arrived, Infinity had more or less been deposed entirely. Hence, he retired from his former position, and decided to take an extended vacation on Gaera, training at his various skills.
He apparently has a 'real name', which he yet to reveal.
His most recent reappearance took place during the events of The Seven Plagues, which involved him intercepting and driving off The Seven Plagues (Mercenary Group) just after her successful slaughtering of Gregory Campbell, Jr. He has remained with Jikuro since this point, perhaps bearing further knowledge of Shamash's intent.