Steven Klain is a thug for hire. Obsessed with combat, but deemed unfit for military service, he joined up with mercenary group Sirius. Klain is an adept fighter, and while Sirius offered him many opportunities to move up in rank, he rejected them, preferring to stay in active field duty. One of Klain's biggest blunders, however, came in the form of the Micronauts, who escaped from a facility Sirius was hired to keep secure. Klain now pursues the diminutive aliens in hopes of once more proving his worth.
Steven Klain was born in Litchfield, Illinois. Klain's parents died in a car accident while bringing him home from the hospital. As such, he was put into the foster care system, bouncing around from foster home to foster home. This lack of stability caused him to distance himself from others.
After leaving high school, Klain had aspirations to join the United States military and become a member of G.I. Joe. However, while he was in perfect fighting condition physically, he was determined to be too emotionally fragile for active duty, and was rejected. This led him to the mercenary organization known as Sirius. Joining Sirius, Klain quickly moved up in rank and became commander for one of Sirius's regional groups. It was at this position he decided to stay, preferring the thick of battle to the safety (and benefits) of a desk job.
Klain's group was hired by Miles Mayhem to guard the scientific facility the Micronauts had been whisked away to following the Revolution event. When the Micronauts escaped with the aid of Rhonda Conway, his team (presumably including Klain himself) pursued them, but were unsuccessful in recapturing the aliens. Back at the lab, Klain chewed out his troops before reporting in to Mayhem. Mayhem reiterated his orders that the Micronauts were to be recaptured alive. Klain's team was able to trace the energy emissions from the Heliopolis, leading them to the miniature city of the Kronus. Klain ordered his men to collect as many "specimens" as possible before setting about to destroy the city. Klain attempted to capture Oziron Rael, but was stopped by Acroyear, who sliced off his index finger and thumb.
Having lost his position in Sirius for his failure, Klain became vengeful and decided to hunt down the Micronauts in order to redeem himself. Billy and was residing with her older sister Betty. Klain captured the family, planning to interrogate Rhonda for any information she might have on the Micronauts. However, before he could begin, he was knocked out by a Weeble as the Micronauts arrived!Klain tracked Rhonda Conway, who had fled her home with her son