The player controls a giant robot which is used to fight another robot in one-on-one combat. Studio Nue (the creators responsible for the mechanical designs for many anime series including The Super Dimension Fortress Macross, Gunbuster, and Mobile Suit Gundam 0083: Stardust Memory) designed the robots in this game. The game is considered a spiritual sequel to Cyberbots: Fullmetal Madness (another fighting game that uses mecha and borrows sprites from the earlier side-scrolling game Armored Warriors). Artwork was done by Sho Sakai and SENSEI, who also did worked on Armored Warriors.
Battles take place mostly on a flat 3D plain, with buildings and other terrain features scattered around. Destroying the terrain (by attacking or walking through them) releases power-ups, which include three weapons (varying between each character/mecha), armor or life powerups, and a power-up, which increases the power of the mecha's attacks, and may also unlock additional abilities or moves.
Rather than rounds, the matches are decided by the life meters of the fighters. Each fighter has two life meters, and is destroyed when the second one is depleted. In addition, each mecha gets an armor gauge that, when broken by consistent brute attacks, lowers the mecha's defense and makes it harder to recover from attacks received.
Each mecha has at least two super attacks, as well as a Final Attack, which is usable when the opponent is down to the last 50% of their second lifebar. This attack, when activated and successfully connected, automatically destroys the opponent, winning the battle.
- G. Kaiser (Kikaioh in Japan) - the main character of the game. This Super Robot attacks with rocket punches, bombs, and a heat beam in its chest. Piloted by Junpei Todoroki . G. Kaiser is based on classic super robots. Particularly Mazinger Z and Great Mazinger. G. Kaiser makes an appearance in the PTX-40A's ending in Tatsunoko vs. Capcom: Ultimate All-Stars.
- Dixen - a mecha armed with a shoulder-mounted beam cannon, grenades, and three remote-controlled beam guns. It can also switch between a beam rifle and a bazooka. Piloted by either Nakato Farland or Halma Frockheart . Dixen is heavily based on the "real robot" anime franchise Mobile Suit Gundam. Even Dixen's Final Attack is a direct homage to the RX-78-2 Gundam's "Final Shooting" scene, with Dixen even concealing it's head and left arm, which were destroyed on the Gundam in said scene.
- Pulsion - An Ultraman-like hero/heroine who transforms into a mecha to fight evil. Pulsion's true identity is either the male Kai or the female Kei. Pulsion was originally a servant of Goldibus who had its memory erased in a fight with Diana-17. Kai has the choice of continuing to fight for justice or return to the evil side, while Kei eventually has to fight an evil version of herself. In Hero Mode, Pulsion adopts a different fighting style that makes it resemble Evangelion Unit 01 in Berserk Mode.
- Rafaga - a transformable fighter, Rafaga can transform from a jet fighter to GERWALK and/or Soldier (mecha) mode. Its pilot, Simon Harvard, is a ladies' man who falls in love with the alien pilot Yale. The Rafagas are heavily based on the VF-1 Valkyries from the real robot series Super Dimensional Fortress Macross. Simon Harvard himself appears to be based on both Maximillion Jenius, and Roy Focker from the same anime.
- Twinzam V - Another Super Robot, it can transform between two forms depending on which is dominant. It is alternately piloted by Daichi Yumeno and his older sister Sora, the two being children who seem to think they're dreaming this all up. Twinzam V is heavily based on Combining Robot anime. Particularly Getter Robo.
- Diana-17 - Diana-17 is a fighting mecha piloted by Reika Amamiya, a student at a girls' academy who is initially the first person to know of Goldibus' plans for invasion in the midst of a war. She tries to gather the other heroes in order to resist the invasion.
- Wise Duck - This huge weapon-laden mecha is piloted by an entire crew, consisting of Gonzales (Commander), Arvin (Combat), Ricky (Gunner), Thomas (Pilot), and Herman (Sonar/Communications).
- Bolon - This patchwork robot, created out of the parts of several buildings, is the creation of Pollin, a Magical Girl who appears to be only about eight years old, though she can age herself to be roughly 17. She has a crush on Junpei, and ends up fighting several of the female pilots in the game over him in her storyline. She is actually the daughter of Goldibus.
- Gourai - A huge red, Samurai-style mecha, complete with sword. Seemingly one of Goldibus' generals, pilot Shadow Red has an agenda of his own. In reality, he is Mamoru Todoroki, the father of Junpei. Shadow Red is notably voiced by Shuichi Ikeda. In Dixen's story, Shadow Red is seen as Dixen-pilot Nakato's rival. This is a reference to Mobile Suit Gundam, in both the Dixen's inspiration by the anime, and Shuichi Ikeda's role as Char Aznable, the masked, red Mobile Suit piloting rival to the RX-78-2 Gundam's pilot Amuro Ray.
- Quvearl - An Octopus-like bio-construct controlled by Yale, a female alien (one of many, as it turns out) who ends up falling for Simon Harvard after he stops her in a battle.
- Gamda - A massive stone golem that seems to be made out of several temples with a huge eye in the middle. It's controlled by Arekshim, an alien ruler with an Egyptian theme.
- Goldibus - the Ultimate Evil. Goldibus has two forms, and must be defeated twice to beat the game. His second form is more powerful and has two menacing special attacks, unlike his less ominous first form.
- Blodia II Custom - (hidden character) - The main mecha from Armored Warriors and Cyberbots: Full Metal Madness. Blodia is piloted by Jin Saotome.