Little is known about the past of Tristan Gregory, but it is known that he was in the U.S. Army for a number of years before he became a mercenary. He was first employed by VIPER to take out a PRIMUS compound in Kansas to prove his worth. After encountering stiff resistance, his goal was met. By detonating their ammo and fuel stockpiles, he was able to completely destroy the compound, but at a cost. The explosion was far larger than he expected and the blast radius engulfed a local farming community, killing a few hundred, innocent people. This fact would have rocked a normal man to the core knowing what they have done to innocent lives, but he didn't care, as long as the job was done. After a few more destructive missions with VIPER, he went to ARGENT, then, I regret to say, us. He is a cruel, cruel man and a talkative lunatic to boot, but he is extremely combat effective and gets the job done every time. He is called Agent Sidewinder because that was going to be his alias when he was expected to join VIPER, but he killed everyone, blew up their camp and took the name just to sound "cool".
Surprisingly enough, Agent Sidewinder was spotted in downtown Millennium City during the recent Qularr Invasion. Reports can be confirmed that he was helping citizens escape to safety away from the invaders instead of shooting them and even helped Ironclad defend Champions HQ during the final battle instead of blowing the building to hell. Maybe there is some good in this man, but we can't be too sure yet.