Roidmude's Core

The Roidmude's Core (ロイミュードのコア), also known simply as Cores (コア), are the essence of the Roidmudes that appear as their given numbers which distinguish themselves from each other (and are pronounced individually; i.e., 029 is Zero-Two-Nine), to which literally ties into their life, acting as their 'soul'. The destruction of a Roidmude's Core results in the permanent death of the Roidmude in question, but if their Core can survive the destruction of their body and be restored later.

Reviving Roidmudes via Cores
Should a Roidmude's Core survive and escape the destruction of it's body, it can fall into the hands of the Roidmude organization, which has several sources for preserving and subsequently reviving Roidmudes.
 * A Roidmude's Core can be absorbed into a Viral Core which matches their Low-Class animal motif. This was performed by Heart who provided a Cobra-Type Viral Core for Roidmude 029 who re-emerged soon after, allowing him to continue and successfully achieve his evolution into an Advanced Roidmude.
 * The tablet device possessed by Brain can, as well as preserving a Roidmude's Core, initiate a reset after absorbing the Core. This was performed on Roidmude 051, a rogue Roidmude whose actions risked compromising their operations and thus was executed by Chase.
 * Medic, who serves as a healer of the Roidmudes, can absorb a damaged Roidmude Core long enough for her to transport it out of harm's way so she can heal the Roidmude and help it reclaim its body uninterrupted. She first performed this on the Gunman Roidmude (018), restoring him shortly after his first destruction at the hands of Kamen Rider Mach, this process was not a reset and allowed 018 to retain his evolved form.

Destroying Cores
The only known way to permanently defeat a Roidmude via the destruction of their Cores is the power of Kamen Riders Drive and Mach, normally via their Full Throttle finishing attacks, but also includes vehicles such as Drive's car, Tridoron. It is still possible for Cores to occasionally survive the destruction of their bodies, though this can be averted by following it up with a direct attack on their Cores before they escape. The first Kamen Rider created by Krim Steinbelt, Proto-Drive, had the power to destroy Roidmude bodies but was unable to destroy their Cores. After being defeated by the Roidmudes, Proto-Drive was converted into Mashin Chaser who is tasked with destroying rogue Roidmudes while leaving their Cores intact, however, it is unknown if Mashin Chaser possesses the ability to destroy Cores.