Eienrai

Eienrai (永遠雷 lit. Undying Thunder) is a powerful entity. First encountered by Gai Nagareboshi in Eighth Release- Azure Thunder Knight, Eienrai's first act is to shatter Kakusei with a touch. Several thousand years ago, he was a famous serial killer known as the "Sōrai no Kishi" (蒼雷の騎士 lit. Azure Thunder Knight). However, during a battle with the Soul King, he was killed and purged of all evil, turning him into a soulless monster with no intent other than to find what he has lost. After several encounters with Gai Nagareboshi's crew, Eienrai realizes what he had been, and becomes horrifed at himself, seeking to atone for his actions, he sets out to destroy Yūrei. Eienrai is also the anti-hero of "A Certain Unlucky Person".