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"However, I’m also a little bit interested in you. If you want to complain to me, my treat. Or you can refuse if you think it’s a trap. But it doesn’t matter either way."

Leon Cromwell, to Rimuru

Leon Cromwell (レオン・クロムウェル Reon Kuromuueru) is an Otherworlder and an ex-Hero who went by the alias Platinum Saber. After he took up the title demon lord, his alias changed to Platinum Devil. He is the ruler of El Dorado, and the seventh seat of the Octagram.


He has long platinum gold hair, blue narrow eyes, a well-defined face, and skin so white that it is almost transparent. He is so beautiful that he is often mistaken for a woman at first glance. Despite his young appearance, he is three hundred years old.


Due to his inability to express himself properly, he is often seen as cold and cruel. In truth he is actually quite kind but his one-track-mind tends to create distance between him and the people around him. For hundreds of years, he's extremely obsessed with Chloe Aubert, his childhood friend, to the extent of willing to commit various atrocities just to reunite with her.

He always shows a proud, cold and calculative personality around other people, even when he's with much more powerful beings like Guy or Velzard. However, his personality drastically changes whenever Chloe is involved, becoming a hotheaded and overprotecting brotherly figure.


Leon was originally an Otherworlder and Chloe Aubert's childhood friend, whom he shared a close sibling-like relationship with. They were caught in the accidental occurrence of a dimensional distortion but then Chloe immediately got summoned to the future, so Leon decided to search for Chloe, managing to make a contract with a Greater Spirit of Light in Ramiris' Dwelling of Spirit and became a Hero.

100 years after coming to this world, became known that Leon self-proclaimed himself as a Demon Lord and, as a consequence, one of the Demon Lords, Curse Lord Kazaream, was furious with him. Kazaream went to slay Leon, but Leon turned the tables on him and defeated Kazaream instead, with him losing his Material Body in the process and being forced to survive for 190 years with his Spiritual Body until he summoned Yuuki Kagurazaka. In the meanwhile, Leon took over Kazaream's castle for himself as his new home base. Due to these events, Leon ended up taking Kagali's place within the Ten Great Demon Lords, and was officially recognized as a Demon Lord.

More than 200 years after coming to this world, during his attempts to summon Chloe, Leon summoned Shizue Izawa out of the Tokyo firebombing and made Ifrit possess her, both in order to save her, but also to find a vessel for Ifrit. Due to Leon's cold exterior, Ifrit making mistaken judgement calls and Shizue's rejection of the world she got summoned to, they were unable to bond properly, culminating in the deaths of Pirino and Pizu, which strained their relationship severely. Ultimately Leon decided to leave Shizue in the care of the Hero Chronoa who appeared at his castle, while Leon himself moved his base over to El Dorado.


  • Rimuru remarked that Leon is the opposite of Masayuki Honjou—everything he does are usually interpreted in a bad way.
  • He tends to have wrong/deviated ideas about Chloe and Rimuru's relationship, making him some type of overprotecting friend, or an overprotecting brother according to Chloe.
  • He usually address himself with the more formal "watashi" (私), but will revert to the informal "ore" (俺) when emotionally charged.
  • As part of his attempt to get Chloe back to his side, he secretly spread the method of (incomplete) summoning around the world, which resulted in many children otherworlders being summoned. Ironically, this is probably how Chloe got summoned into the future in the first place.
  • Leon’s surname, Cromwell, derives from the two Old English words crumb and well, which together mean “bent stream”. This surname hails from Nottinghamshire and West Yorkshire in England. Two of the most famous people to have borne this surname were Thomas Cromwell: chief minister of King Henry VIII of England from 1534 to 1540, and his great-nephew, Oliver Cromwell: Puritan leader and commander of the Roundheads during the English Civil War, and subsequently ruled the British Isles as Lord Protector from 1653 until his death in 1658.