"Charles, if you're able to obtain the Heart of Darkness as a promotion material, it won't absorb the souls contained within. Instead, it will allow them to be liberated," Theodore said seriously, locking eyes with Charles. As he spoke, he handed over an ancient tome.
Charles reached out and took the book, carefully flipping through its pages. He found that the information indeed matched what Theodore had told him.
There had once been a Dark Attribute Beast Master who, in order to promote their mystical beast, sought out an Evil Organization branch that specialized in creating Dark Altars. After killing everyone inside, the Beast Master's mystical beast absorbed the Dark Altar, and the tortured souls that had been trapped within it were all freed.