|Appearance(s)||Armored Core 2|
|Back Unit R||Grenade Launcher|
|Back Unit L||Multi Missile|
|Arm Unit R||KARASAWA Laser Rifle|
|Arm Unit L||Laser Blade|
- "I'm a realist, not some fool. All that I've wanted to do was to revive the ways of old."
- — Klein to The Raven
Leos Klein was the leader of the Frighteners during the events of Armored Core 2. He was also known to have been a Nine Breaker in the Arena of the original Ravens' Nest. He serves as the primary antagonist throughout the game.
Ninety years old at the beginning of Armored Core 2, Klein has been alive from the first era of Armored Cores and has been kept alive due to cybernetic enhancements, having worked at the first Mars terraforming project. At the beginning of Armored Core 2, he is working for LCC at The Earth Government's behest and leads the Special Forces.
Leos eventually leads a coup d'etat against LCC, destroying them in the process. Subsequent to this, he activates the unmanned Disorder Units, which attacked the corporations on Mars, destroying them. Following this, Leos steals Balena's S.T.A.I. Battleship and heads to Phobos, in actuality an alien super-weapon, activating the weapons system and threatening to plunge the artificial moon into Mars. However, The Raven defeats Leos, who is piloting a Martian Superweapon, before his plan can come to fruition. It is unknown what Leos Klein's ultimate fate is, but it is possible that he was killed as Phobos disintegrated in Mars' atmosphere.
Klein pilots an AC which is identical to the AC on the front cover of AC2. The only difference is that the unit mounts different weapons. The energy shield is replaced with the MOONLIGHT laser blade and the laser cannon is replaced with a grenade launcher. It also equips anti missile extensions, a multi-missile launcher, the KARASAWA laser rifle and an overboost core. Due to the Human PLUS enhancements of the pilot the unit can fire the back mounted grenade launcher while moving and fire blade waves. It also is capable of ignoring weight restrictions. Kleins AC also has a nearly identical decoy AC appearing in the mission Eliminate Leos Klein and is known as the AC Klein Fake. After the destruction of Kleins AC in the mission Infiltrate STAI Battleship and upon arriving on Phobos, he uses the Scarabaeus and later the Filial in the final mission to fight the Raven.
The real Klein is dangerous namely because of his powerful weaponry, the close quarters and the fact that you may be hurting from Boyle's fight. The best way to kill him is quad legs and KARASAWA due to it being a very effective combo in the game. He falls quick enough as long as the AC can survive.
- "Let's fight, Raven. We'll settle this in battle."
- "You remind me of another pilot I knew long ago... A rebel... I've already figured someone like you into my calculation. It's my intention that you do not interfere with my plans."
- "Raven... It's not over yet. ...Phobos... That is where I'll be reborn."
- "We all make mistakes. Don't you think, Raven? We humans need strict supervision. We cannot live on our own. A state dedicated solely to Ravens... I'm a realist, not some fool. All that I've wanted to do was to revive the ways of old... Die, rebel!!"
- "Ra...ven... Destroy...the orbit-control...mechanism... Phobos will...stop when you do so..."
- "Raven... What is it that you wish?"
- Head: ZHD-MO/EGRET
- Core: ZCL-XA/2
- Arms: ZAN-202/TEM
- Legs: ZLN-XA2/FF
- Booster: Unknown
- FCS: Unknown
- Generator: Unknown
- Radiator: Unknown
- Inside: Unknown
- Extension: ZEX-RS/HOUND
- Back Unit R: EWC-GN44-AC
- Back Unit L: ZWM-M24/IMU
- Arm Unit R: KARASAWA-MK2
- Arm Unit L: LS-MOONLIGHT
- According to the Japanese site from the time the game was released, he is in fact the original Nine Breaker (i.e. The Raven from Master of Arena, who defeated Nine-Ball, the original top Raven both in the Arena and on the battlefield). This would make him at least 90 years old at the time of his insurrection.
- Canonically, before switching to the Ethermaster, he previously piloted the Annihilator during his time in the events of Master of Arena.
- In a throwback to the first Armored Core game, Leos Klein's final words are similar to that of Hustler One in Destroy Floating Mines (if the player destroyed both Nine-Balls). See last quote above.
- In the Japanese version of the game, Leos Klein is voiced by Koyama Rikiya.