The original Firefall was Karas from Galador. He was a childhood friend of Rom. At some point in their youth Karas saved Rom from drowning, creating a deep bond between them. Rom considered Karas his "brother". When both men became Spaceknights they fought side-by-side. Karas' power was to control the "Living Flame" of Galador.. However Karas was too impatient to fight the Dire Wraiths. He went ahead of the other Spaceknights in a battle early in the conflict and his tracks were lost. He was reported "missing in action", presumed deceased. Karas had actually been captured by the Dire Wraiths who were trying to find a way to use him against other Spaceknights. Karas used his power to send his consciousness and human body to Limbo. He was seen still trapped there in Rom #19. He is presumed still trapped there.
The Dire Wraiths kept the Firefall armor but it proved useless without a mind bonded to it. Two centuries later they bonded the armor to Archie Stryker, an Earth human. Stryker was a veteran soldier of the Korean War with considerable combat training. But in the decades that followed the War, Stryker had become a common criminal. In Rom #2, Stryker and his gang were robbing a shop and holding its manager at gunpoint when Rom entered and killed said manager. Rom also incapacitated the criminals. The manager was a Dire Wraith in human form but Stryker was still convinced the guy was human and Rom a cold-blooded murderer. He swore to find a way to destroy Rom. This piqued the interest of the local police chief arresting Stryker, another Dire Wraith in disguise. He saw potential in Stryker as a pawn. When the police chief was also killed by Rom, Stryker became convinced Rom was a serial killer.
Stryker was recruited by the Dire Wraiths to fight Rom. The Wraiths posed as representatives of the United States government and Stryker was convinced he was fighting another "just war". In Rom #3-4, Stryker was bonded to the Firefall armor and fought Rom as planned. Rom both defeated Stryker and managed to explain what was actually going on. However the Wraiths still controlled Stryker through their magic. In Rom #11, Stryker was able to "free" himself by throwing himself at a Dire Wraith trap set for Rom, effectively committing suicide but rescuing Rom in the process. In Marvel Two-In-One #99, the armor was controlled by magic but had no user bonded to it. The armor was destroyed in battle.
The third Firefall was Tarn, a Galadorian youth recruited as a third generation Spaceknight. This generation included two sons of Rom and Starshine/Brandy Clark and various Galadorian youths originating in Galador's space colonies. The colonies had not been affected by the civil war which annihilated the previous inhabitants of Galador. His main power was use of plasma fire. The main difference of these Spaceknights was that they could change between cyborg and human form at will. The first two generations could only regularly use the cyborg form, their human form was placed in suspended animation to await their returns.