Red Faction: Armageddon takes place 50 years after the events of Red Faction: Guerrilla and is set on Mars. The player assumes the role of Darius Mason, a well-meaning individual who wants to benefit his people. Unfortunately, it's not just his fault that a terrorist destroys the machine maintaining a human-friendly atmosphere, forcing humans to retreat underground. He also mistakenly unleashes an hostile alien race. As a result, surviving humans aren't pleased with his actions, and he must now venture into the tunnels to set things right!
The game is a linear third-person shooter with a focus on action and adventure gameplay. The majority of the game involves walking through levels, killing alien masses or human cultists using a mix of conventional and science fiction weapons. Occasionally, there are boss battles and vehicle sequences, such as inside a mech. In the levels, players can find valuable pieces of scrap to trade for character or weapon upgrades. The destructible terrain returns, allowing players to use it to dispose of enemies. A device also allows Darius to repair his environment.
The game features two additional playing modes. The destruction mode aims to earn as many points as possible within a limited time frame by destroying the environment. The second mode is designed for cooperative play with up to four players, where the objective is to fight off enemy waves.