He later became a Demi God during the Great Tenma War.
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.
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.
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.
Through Yuuki's machinations, Footman, one of Kazaeam's subordinates fought Leon piercing his heart. Rimuru via Ciel repaired his heart, upgrading him to a Demigod.
- His subordinates are reminiscent of the Super Sentai Warriors due to their color scheme.