The Roidmude's Core (ロイミュードのコア Roimyūdo no Koa), also known simply as Cores (コア Koa), 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, they can be restored later.