Zen was originally a being from the Sea of Souls named Chronos, an avatar of Death created by the collective will of humanity. In the course of his duties, he appeared to the ghost of a girl named Niko, informing her of her demise and her need to come with him. To his confusion, however, Niko was silent, neither struggling against him or welcoming his presence. On a whim, he delved into her memories to see if he could make her speak, and after seeing her despair.