The knockdown, also known as system failure, is a very important aspect of battling in custom robo. A knockdown occurs whenever a robo sustains enough damage, and also when the robo's HP becomes zero. This is dependent on the robo's endurance, which varies from robo to robo, and also the down stat of the weapon. When a robo is knocked down, it is vulnerable to attack for a few seconds; however, any attacks on a downed robo are significantly weakened, typically by 70%, though this percentage is believed to decrease while the robo recovers. After recovering, the robo enters the Rebirth stage. Some illegal robos like Rahu III and Jameson are resistant to knockdowns.