Sinister Connections

At some unspecified time during Gambit's roaming, his mutant ability to charge matter with kinetic energy became so powerful that he was unable to control it. An acquaintance of his, Grey Crow (better known as Scalphunter), probably introduced him to Sinister at this point, suggesting that the scientist could help Gambit. Unfortunately, Sinister, although successful in getting Gambit's powers under control through brain surgery, demanded a terrible price in return for his services.

Initially, all seemed well as Gambit stole items for Sinister, who was obviously very pleased with his work. However, he was then contracted to gather a group of mercenaries together for Sinister who would later be known as the Marauders. (This also explains the connection with Sabretooth that was intimated in early appearances.) Ironically, his sense of honor lead him to feel it was necessary to repay Sinister, forced him to temporarily overlook the very criminal nature of the mercenaries he was gathering. To indicate that the debt was repaid, Sinister gave him the silver vial, which probably contained whatever he had removed from Gambit to dampen his powers. Although he speculated it would mean some illegal activity, it's clear he really knew nothing about Sinister's real plans and didn't want to know any more than he did.

Gambit was breaking off their arrangement when Sinister asked him to do one more job saying he knew Gambit's price to do it, but this "price" has not been revealed.

Evidently, however, Sinister offered him something he could not refuse as Gambit agree and ended up leading the Marauders into the Morlock tunnels. It is unclear if Gambit was with them when they left Los Angeles. The Marauders originally had been shown following the Morlock, Tommy, to New York and into the Morlock tunnels. He may have met them there, after they'd killed her. Gambit believed that it was big heist or something where killing could likely occur if necessary but never suspected the resulting massacre of men, women, and children. He later admitted that he had a bad feeling about the job, but had told himself to ignore it, this was a job he needed to do.

Regardless, when he found out what was happening, he tried to stop the Marauders. Sabretooth attacked Gambit and left him for dead, but he managed to escape, even saving the Morlock child, Sarah, who later became Marrow. Despite his interest in Gambit and admiration for his skills, Sinister apparently considered him expendable for this job, probably because he had told Sinister he wanted to leave his employ.

Gambit was sickened, both physically and mentally, by the Morlock Massacre and after that it seems he spent much time trying to make up for his mistake.

This seems to have been a few years later since Gambit had already been involved with Spat and Grovel prior to then. It is also obvious that Gambit didn't like Sinister or the work and didn't want to do his bidding, but there are hints from Sinister that at some time he helped Gambit out. It is unclear when this was (it is even possible this is from Remy's childhood) or if it has some connection to Sinister's theater in Seattle (Essex Theater, named after him) or if that was just their meeting place. While it is apparent that Gambit considers them "squared away" for now however Sinister hints that Gambit will always be tied to him.

Sinister has even shown some concern for Gambit, an emotion he's not displayed for anyone else besides Scott Summers or his own long-dead son and wife.

Sinister didn't seem to have any interest in Gambit in the Age of Apocalypse series, but that may only have been because he couldn't catch up with him there.