Demon Lord Leon Cromwell [レオン・クロムウェル, Reon Kuromuweru] is a True Hero and one of Eight Star Demon Lords. He is also called the Blonde Demon.

He later became a Demi God during the Great Tenma War.


He doesn’t take men for partners. Even among women he only goes for the ones he desires.

His skill of evading the point is rather superb.


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.


Leon was originally a world traveler who was Chloe O’Bell's childhood friend. They were caught in the accidental occurrence of a dimensional distortion but Leon appeared in the world alone. He decided to search for Chloe and obtained the Hero's egg due to his desire to protect her.

He is the last born Demon Lord, the human “Demon Lord” Leon Cromwell. He with his overwhelming magical power rules over his increased number of Majin, he identifies himself as the Demon Lord of the frontier.

One of the Demon Lords, was furious with him, the Demon Lord Kazaream had waged war against him. But he was beaten by Leon instead. It was also by Leon’s own hands. Due to this, Leon's "Hero's egg" hatched and he awakened as a true hero. In response to the situation, the other Demon Lords, not knowing that Leon is a hero, recognized him as a new Demon Lord.


He obtained Luck Blessing from Ramiris.


  • Spatial Movement Magic

Ultimate skills

  • Purity King Metatron
    • An ability which draws purest energy possible from power, magic, aura, and skill
    • Holy Breakdown (36 th Style Annihilation’s Light of Holy Spirit Purification)
    • Triangle Pyramid (Sacred Tetrahedron Demon Sealing Barrier)


  • Flame Pillar (Holy Flame Rapier): Mythical class (Gods) rapier, the strongest sword in Leon’s possession.
  • Golden Circle (Golden Round Shield): legend class shield.



He isn’t on good terms with Ramiris. From the very moment they met he had thought to kill her a few times.

Chloe O’Bell

She is a childhood friend of Leon, a best friend. An existence he loved like a sister, his everything.

Shizue Izawa

She was summoned instead of Chloe and gave her Flame Giant Ifrit to save her life.

Rimuru Tempest

Rimuru initially disliked him because of treatment of Shizue but after realizing that he actually, in fact, saved the latter's life, Rimuru cooperated with him. They also cooperated with one another several times. He fully trusts that he can leave Chloe in Rimuru's hands. During the Great Tenma War, he evolved into a Demi-God when Rimuru reconstructed his core to revive him.






  • His subordinates are reminiscent of the Super Sentai Warriors due to their color scheme.


Tensei Shitara Slime datta ken Wiki has a collection of images and media related to Leon Cromwell.