High-Speed Regeneration (고속 재생, lit. "Ultra-Fast Regeneration") is a superhuman ability possessed by werewolves, as well as M-21, a modified human. It is the signature ability of Werewolves, As mind control is to Nobles.
High-speed regeneration allows a person to recover from any damage that they sustain by causing their cells to repair themselves at an incredible rate, closing the wounds on their body and causing any limbs that they have lost to grow back. While High-Speed Regeneration is indeed a powerful ability, it is not without its flaws. Despite the extent to which it can heal the body, internal organs such as the brain cannot be regenerated; if such irreparable damage is sustained, the rest of the body can continue to regenerate, though to no avail. In addition, if the body is damaged before it has the chance to heal, or if enough damage is inflicted on it at once, then it can be destroyed. It is shown that, after being attacked by the Nobles, whom have usual imbued power, M-21's regeneration was slowed considerably.