In ca. 3018 or 3018, Kellen Folker was a veteran MechWarrior with the Guardians of Cameron mercenary unit. When the unit fought House Marik raiders on Furillo, Folker was fired at from a village and went on a rampage, destroying half of the town and killing an unspecified but implicitly high number of civilians. He was court-martialed and drummed out of the unit on testimony from Davis McCall, then a green MechWarrior recruit and member of Folker's lance.
Folker subsequently garnered a reputation as a hard-case freelancer who would do anything for a price. It was remarked that he and McCall later ran into each other again on Gladius, though no details are given about this encounter.
By 3056, Armed Forces of the Federated Commonwealth Major Kellen Folker served as senior military advisor to Nelson Wilmarth, the governor of Caledonia. Wilmarth was an unloved offworlder who took extreme measures against the protesting population such as deploying BattleMechs against civilian protesters, torturing prisoners to death, and publicly displaying heads and bodies on pikes. Folker personally piloted a Wasp, and in one instance, his 'Mech stepped on and killed a protester.
The actual military power on Caledonia, and implicitly also administrative power, rested with Folker, who was in fact working for a cabal of rebels around Field Marshal Brandal Gareth and "pulling Wilmarth's strings" for them. In this role, Folker was deliberately fanning the flames of revolt on Caledonia.
Folker was briefly taken hostage by Davis McCall when a meeting at Wilmarth's citadel turned into a confrontation and McCall, together with Alexander Carlyle and some freed prisoners, had to force their way out. He was later released, after being fed misleading information.
When the Gray Death Legion proper was deployed to Caledonia to subdue the ongoing uprising, Folker was waiting for Grayson Carlyle and his troops in a ST-46 shuttle at the zenith jump point. They met aboard the JumpShip Rubicon, where Folker introduced himself as the governor's AFFC liaison and confronted Carlyle with evidence implicating Davis McCall and Carlyle's son Alexander in attacks against Wilmarth's government (which the Legion was supposed to support). He rode down to the planet with Carlyle aboard the Legion DropShip Endeavor and upon arrival at the New Edinburgh starport on 13 April 3056, he ordered Carlyle to deploy his 'Mechs against the civilian protesters in the streets. When Carlyle refused the order, Folker had him arrested and announced that he would assume control of the Gray Death Legion, but within minutes Carlyle's security detail freed him arrested Folker and his adjutants. Folker in turn escaped when an explosion shook the terminal building during the riots. He was not heard from again, and thought to have left the planet when the Gray Death Legion ejected Wilmarth's forces from Caledonia.