Leon Cromwell

Leon Cromwell is one of the Octagram (the eight Demon Lords) in the anime That Time I Got Reincarnated as a Slime. He is also known as the "Platinum Devil" or "Blonde Devil."

In the anime adaptation (across Seasons 1–3 and related specials), Leon is portrayed as a powerful Otherworlder and former Chosen Hero who became a Demon Lord. He has long platinum-blond hair, narrow blue eyes, pale skin, and strikingly handsome, almost androgynous features that can make him appear feminine at times.

Personality-wise, he comes across as cold, laid-back, aloof, and somewhat indifferent to things like Demon Lord titles or politics—he doesn't seem to care much about status or drama. This distant demeanor often makes him seem cruel or unapproachable, though deeper context (especially tied to his past actions and motivations) hints at a more complex, even kind side beneath the surface.

He first appears prominently in connection to Shizu (the masked adventurer), as he was the one who summoned her from another world and bound the spirit Ifrit to her, leading to key events in Rimuru's early story. Leon rules over his own territory and occasionally interacts with other major characters like Rimuru during events such as Walpurgis.