Five years after the coup attempt led by Leos Klein the Earth government struggles to realize one of its original objectives, relocating people from the underground cities to the Earth's surface. These plans are hopelessly delayed because the government has had to shift its focus from resettlement to military buildup. A necessary move in the government's eyes, needed to keep both the corporations and the situation on Mars in check. After facing various setbacks, the corporations that once held sway on Mars are in positions of diminished influence. This does not sit well with them and each is secretly rebuilding their personal armies in order to contend with the government's growing might. Tensions between the corporations and government are at a breaking point. With all of the government's efforts currently focused elsewhere, resentment toward the institution from the general populace is at an all time high. Tired of being neglected, people living in the underground cities have taken matters into their own hands and incidents of armed revolt are a daily occurrence.
- Zio Matrix - Following a failed coup attempt (through which Zio hoped to strengthen its power base by exploiting Disorder technology), the parent company sidestepped most repercussions by discreetly transferring blame to its Mars division, claiming it acted alone. Even so, Zio Matrix now toes a fine line with the government and is more circumspect in its dealings.
- Emeraude - After an all-out clash with the LCC on Mars, Emeraude's position has been significantly weakened. In a bid to combat the government's increasing influence and regain lost ground, Emeraude actively pursues confrontation and is the most volatile corporate element.
- Balena - Due to the Frighteners overstepping their authority, Balena and the LCC's efforts to reshuffle the power structure on Mars failed. Balena's ties with both Zio and Emeraude are all but severed, now that the company's involvement with the government is public knowledge. Balena continues to provide assistance to the government, but it is also secretly backing the Indies rebel group.
- The Earth Government - Under the tagline "The Central Union of Earth", the Earth government is exactly what its name suggests it is; a singular governmental body serving the entire planet. After the end of the subterranean era and the downfall of the Earth-based corporations the government rebuilt itself into the ruling body it was prior to the "Great Destruction". The government relies primarily on proxies like the Bureaus of Control and the LCC to govern locally while it focuses on the environmental reclamation and the re-population of Earth's surface. After being betrayed by the Frighteners, the government has become reluctant to employ Ravens unless circumstances are dire and Ravens are not allowed to enter Earth Central, the capital city of Earth.
- Bureaus of Control (BOC) - Administrative bodies set in place by the government. BOC's exist in all major Earth cities and are tasked with supervising development, regulating corporate activity, and maintaining order in their respective cities and the surrounding areas. Bureau names indicate their area of jurisdiction, for example, Neo Isaac Bureau of Control.
- Nerves Concord - The Nerves Concord continues its role as both Arena operator and impartial middleman between the corporations and Ravens. Though siding with no one, the Nerves Concord's function perpetuates corporate rivalries.
- Indies - A large, well-financed rebel group that plots against both the government and corporations in a bid to overthrow them and establish a new governing body. Its ranks consist mainly of the poor and disenfranchised, but a number of Ravens have taken up the cause as well.
The expansion to Armored Core 2 runs on the same game engine as its predecessor but features a number of changes in the way the game is played, namely the fact that the player can tell if a target is behind cover when the lock on indicator turns green. There is no trial mission in Another Age that kicks the game off, the player is simply thrown into the world with their AC and their first job offer right there waiting for them. The Arena, which played a significant role in Armored Core 2 has been scaled back a bit, but a fair number of the game's missions involve one-on-one combat with other Ravens in a set-up not unlike Armored Core 2's Arena. Another Age has sparse expressed plot, it is more a portrait of the life of a mercenary, always bouncing about from place to place and not getting tied down to any one particular cause. Occasionally recurring elements pop up from time to time as the game progresses, but there is no defined storyline to the game. While there is virtually no storyline, there a total of 103 missions that make up the mass of the game, the largest Armored Core title to date, and each mission plays out in a specific area of the world map screen that would reappear in following AC titles down the road. Another Age is also noted for its cameo appearances. Past enemies from the PS1 era games Stinger (both Vixen and Phantasma) and Nineball appear as bosses in several special missions that are unlocked once you clear all 100 of the game's missions.
- -1 - Quartz Clock, an AI Ranker from Armored Core: Last Raven, uses a replica of Wonder Raid, the AC that appears on the cover and the intro video of the game.
- All of the equipment that had to previously be unlocked in Armored Core 2 is available from the start of the game.
- Missions in Armored Core 2: Another Age
- Enemies in Armored Core 2: Another Age
- Parts in Armored Core 2: Another Age
- Armored Core 2: Another Age Ravens