Leos Klein appeared in Armored Core 2
as leader of the enigmatic Frighteners. Although the full extent of his agenda remains unknown, he lead an uprising on Mars and activated an ancient alien orbital weapon - seemingly to destroy the planet - before he was stopped by the player.
Klein was raised in Isaac City, part of a contested region in the crosshairs of mega-corporations Chrome and Murakumo. As part of the escalating mercenary violence in the sector, the Raven AC Nine Ball razed the city. Although Klein survived his family did not.
Coming of age, Klein joined the Raven's Nest in an attempt to seek out and exact revenge on the pilot of Nine Ball. These events are chronicled in Armored Core: Master of Arena. It turned out that the Hustler One, the unit's pilot, was the then-current top ranking Raven and the Nest protected its interest by impeding Klein's progress at every step.
Eventually, Leos Klein destroyed Nine Ball and was the first holder of the now-legendary title 'Nine-Breaker'. In the years following his ascent, Klein was instrumental in the downfall of the Raven's Nest.
Mars & The Frighteners
As the big corporations, industries and governments shifted to Mars, so too did Klein. In his 90s, but coaxed out of retirement to head up the LCC's security unit, he foresaw a new era of strife and corporate infighting like the one that lead to the destruction of Isaac City and the Great Destruction before it.
Vowing to steer humanity's course away from another cataclysm, Leos Klein left the LCC and founded the terrorist organization known as 'The Frighteners'. As part of his campaign against the Martian colony he resurrected and unleashed an army of Disorder units - mechanic remnants of an ancient civilization - on the surface. In the chaos that followed he commandeered the massive STAI battleship but his plans were thwarted by the player, an agent of the new Nerves Concord.
Retreating to Mars' moon Phobos, Klein activated the battlestation which reveals the moon to be an alien orbital weapon. Before it could be fully armed, his plans were again set awry by the player, who faced Klein in an AC-based massive alien weapon. Emerging victorious, the player shut down the battlestation and set the moon on a decaying orbit.
Leos Klein is believed dead following his defeat on Phobos.
- Klein is in his 90s during the events of Armored Core 2. It is highly probably he was a product of Human PLUS experiments, explaining his abilities so late in life.
- Although not identified in English versions by name as the player character from Master of the Arena, various Japanese sources confirm this relationship.
- Leos Klein pilots an Ethermaster AC, a high-end mass production unit from Zio Matrix with red livery (a blue version is seen in the AC2 intro movie). His armament includes the Karasawa rifle, the Moonlight blade, a grenade cannon and a missile pod. Choice of weaponry includes mostly the same weapon types as Nine Ball.
- Except for the head unit, Klein's AC is very similar to Providence, piloted by Ares, the current Nine-Breaker circa AC2. There is speculation that the similarities may not be coincidental.
- Leos Klein and Hustler One are the only characters in all of Armored Core to appear in more than one generation of games.