Everything seems to be running smoothly until Vile, who was last seen in Mega Man X3, returns and kidnaps Lumine, causing Maverick uprisings all over the world. While battling the Mavericks, the Hunters pick up hints that Sigma has returned and teasing a concept called "the new world". Eventually, Sigma is tracked to the Moon, where he unveils his ultimate plan: eradicate the "old generation" and re-populate it with his "children". He reveals all of the new generation Reploids contain a copy chip which possesses his DNA, meaning these 'virus-proof' Reploids are essentially copies of Sigma.
When Sigma is defeated, Lumine emerges from the shadows and congratulates the Hunters on finally destroying Sigma once and for all, before admitting he was manipulating Sigma in order to get his DNA and is behind the entire plot. Lumine gloats to the stunned Hunters that in order for evolution to take its course, he and the new generation Reploids must destroy both the humans and "obsolete" Reploids. After a massive struggle, Lumine is defeated, but he warns them that it is too late to stop what has already begun. As Axl approaches Lumine's body, a tentacle springs from it and breaks the crystal on his helmet, knocking him unconscious.
The ending of the game varies slightly depending on which character defeats Lumine. As the Hunters ride back down the orbital elevator, Zero wonders if he no longer has to fight now that Sigma is dead for good, while X ponders Lumine's words on evolution. Zero tells X not to let his words get to him, as new generation Reploids becoming Sigma could hardly be called evolution. Furthermore, he tells X that even if they are destined to join the scrap heap when that evolution does comes about, they'll still have to fight, not only against the Mavericks, but against their own destinies as well.
A post-credits scene explains that Lumine's death and the news of him becoming Maverick resulted in ceasing production of DNA copy chips. However, due to the increasing need of advanced Reploids for space development, production resumed several years later, despite the objections of many. Meanwhile, as the Hunters continue to descend the orbital elevator, a faint purple light emits from Axl's shattered helmet crystal, suggesting that Lumine's spirit lives on.
Gameplay
Overall gameplay in Mega Man X8 is mostly similar to previous Mega Man X games and has removed the 3D style from Mega Man X7 in favor of a 2.5D style, although two of the stages, namely "Central White" and "Dynasty", are fully 3D, played aboard a vehicle with a close third-person view. After an introductory stage, Mega Man X8 presents the player with a choice of 8 stages, with a Maverick robot serving as the stage boss. After defeating the 8 bosses, a series of fortress stages open up for the player to complete in linear progression until the final boss is defeated. This game also has an option of three difficulty modes, with slight differences between each mode. Normal or hard mode is recommended if players want to observe the ending and fight the "real" final boss.
The player starts the game with access to three playable characters: X, a shooter able to wear multiple armors that can be mixed and matched which opens up possibilities for customizing x's abilities, Axl, a shooter able to transform into enemies and fire in any direction; and Zero, a sword fighter able to double jump. Additionally, Zero can equip additional weapons that can be purchased as chips at the store such as hammers,fans and additional swords after finding a certain rare metal for it, excluding one of the weapons which is only available for purchase upon completing the game with Zero or entering a code in the title screen of the PlayStation 2 and Mega Man X Legacy Collection 2 versions. Axl's gameplay had been slightly reworked to make him more different from X, such as gaining the ability to acquire new guns after defeating each boss, instead of gaining their weapon and can fire in any direction. X8 introduces new mechanics to the game; the first is Guard Break, which can break enemy defenses when enemies are attacked with certain weapons. The second is Double Attack, where the playable character and the chosen partner character perform a screen-filling attack that causes heavy damage to all enemies on screen. Additionally, X's new armor, the Neutral Armor, can be customized with parts that can either form two new armors the Icarus or Hermes armor, or mixed together for different effects. However, mixed parts of armors are not as effective as complete armors which lack the Giga attack ability, forcing players to choose wisely when building armors.
Two characters can be selected to go to a stage, while a navigator can be assigned to assist the player. Depending on the navigator's qualities, the character will be informed about the stages' hidden paths or boss weaknesses. In every stage, the characters can obtain items that can be used in a shop to buy upgrades. The three navigators can also be unlocked as the playable characters by buying chips after completing the game in the Normal or Hard levels or entering the code in the title screen of the PlayStation 2 version and later Mega Man X Legacy Collection 2 re-release.
Much like with X7, this game is also equipped with New Game Plus features, which allow players to start a new game from an old save file upon completion of the previous game. Aside from the aforementioned unlockable features, all chips that were purchased in the store during the previous game are retained. Players also have the option of starting fresh by deleting any of these chips and repurchasing them later.
Reception
Mega Man X8 received a generally mixed to average reception. It was generally praised for returning to a more classic style of Mega Man gameplay and removing the criticized gameplay elements of Mega Man X7. IGN praised the game for its mixture of 2D and 3D, and its camera system, saying "Thankfully the transition from one plane to another is pretty seamless and isn't the bothersome chore that switches in X7 were. It's an easy and totally acceptable gameplay method and one that should have been used in 2003 to begin with." On the other hand, GameSpot criticized the game for its level design, which often made the game extremely frustrating to play. They also derided the story, remarking that it "dabbles in a lot of nonsensical anime-style ramblings about things that are of little importance to the actual game."
According to Famitsu, Mega Man X8 was the tenth best-selling game in Japan during its week of release at 14,927 units. A total of 35,546 units were sold in the region by the end of 2005.
