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Apocalypse Arm is Robo's strongest Mechanical Arm in Chrono Trigger, exclusive to the DS release of the game. Found in a chest in the Dimensional Vortex (Future). Ordinarily modifying attack by zero points, Apocalypse Arm deals 9,999 damage with each successful critical hit. This weapon has a critical hit rate of 10%. Equipping the Rage Band adds a 50% counter attack rate, thus it increases the potential that this weapon will achieve its special effect when worn by Robo. Additionally, the Dragon's Tear accessory, while exclusive to Chrono Trigger (DS), also grants bonuses to critical hit, making it a desirable pair for this weapon as well.
The Apocalypse is a major geologic catastrophe following the Rapture in Christian traditions. Also, interestingly enough, Robo is from a time period rendered desolation by an apocalyptic catastrophe that occurred in the year 1999 A.D. in the Keystone Timeline.