Leon Cromwell | Reincarnated As A Slime


Leon Cromwell (Reon Kuromuueru) is an Otherworlder who became an ex-Hero, going by the alias of Platinum Saber. This was changed after he became a “Demon Lord,” making it Platinum Devil. He is the founder and current ruler of El Dorado.

Leon Cromwell Reincarnated As a Slime Wiki

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Leon Cromwell

Leon Cromwell

Character Information

Position in Anime: Demon Lord

Gender: Male

Species: Demonoid

Age: 300+

Hair Color: Blonde

Professional Status

Occupation: – Ruler of El Dorado
– Demon Lord

Affiliations: Octagram

Appearances in ANIME/MANGA

Manga debut: Chapter 9, Chapter 76

Anime debut: Episode 6

Voice Actors

Japanese: Jun Fukuyama
English: Christopher Wehkamp


Leon Cromwell Appearance

Leon Cromwell possesses the appearance of someone who is serious and somewhat ominous. His hair is of a pale silvery-blonde gold color and his good-looking face has a pair of blue narrow eyes. His skin is also so white that he can be mistaken for being young; a change of clothes can even make him look like a girl. Despite this, his age is over 300 years old.

His usual attire features a black overcoat that trails as he moves; his inner clothing has the resemblance of a priest robe with gray and yellow patterns.


Leon Cromwell

Leon is actually a soft boy at heart, but due to certain events and him not being able to express himself, he is seen as someone who is cold and even cruel. His cynical personality led him to focus on one and only one thing, to reunite with his childhood friend, Chloe Aubert. Due to this, he has maintained a distance from other people in order to attain his goal.

Strengths and Skills

Leon Cromwell


Leon Cromwell has a variety of skills and abilities that contribute to his overall strength. For once, he is superior to arch demons for being the “Demon Lord.”

From the source material, the web novel, it was mentioned that arch demons are pre-Demon Lord class (considered as A+ in rank), said to be able to destroy towns [ch70] and small countries [ch147]. As seen from the perspective of an Otherworlder, their magic attack can be compared to a tactical nuclear weapon. [ch 147]

demon lord Leon

One of Rimuru’s arch demons, Ultima, released nuclear flame magic that wiped out an entire fleet of airships (90+ airships) and sent shrapnel and debris flying everywhere. This example gives a better sense of scale on how powerful arch demons are.

During his fight with Yuuki, lightning formed from both of their auras said to have flashed between the heavens and the earth [ch133]. It also led to the ground shaking and breaking, along with the other land near to them [ch134].

This fight even caused a 4.0 earthquake on the deformed land and destroyed mountains [ch135].

With all of this, it can easily be assumed that can easily destroy the whole place of El Dorado if he decided to go all out [ch203]. (In chapter 130, El Dorado was said to be the size of a continent.)

Speed and endurance

Speed and Endurance

His attack is similar to Hinata’s “Disintegration [ch132],” a SoL technique that attacks the opponent on the atomic level [ch66]. Upon release, his magic turns into light (using photons/light) that attacks the target [ch133].

He is also usually striking with attacks that are near the speed of light with his sword thrust [ch134].

For his endurance, he was able to fight against Kazaream for a full day and night. And even after that lengthy battle, he showed no sign of exhaustion [ch210].

Leon Cromwell Skills

Some Other Skills

Besides firing huge waves of light through his hands, he also has an ultimate skill; the King of Purity Metatron. A very powerful attack that draws the purest energy possible from one’s power, magic, aura, and skill [ch133].

His ultimate is mentioned to be the “apex of light-based abilities and magic [ch133].

  • Able to use spatial travel [ch78]. (A way to open a “door” to another place [ch103].”)
  • Able to fly [ch132].
  • Able to use a barrier that is like the Infinite Prison, and has a 100% chance to seal demonic beings. It’s called the “Sacred Tetrahedron Demon Sealing Barrier [ch134].
  • Holy Breakdown- a barrier that is inescapable to opponents trapped within it. After activation, it annihilates anything inside the barrier, while releasing a thousand times more power than Disintegration.
Flame Pillar

He can summon the “flame pillar + golden circle”, a sword and a shield set- including a rapier that is considered as a God-class weapon that has exponentially larger damage when used against entities with demonic attributes.  The shield is said to reduce dark attacks by half.


  • Leon Cromwell’s kind is categorized as “Stray otherworlder.”
  • He currently lives in “El Dorado,” and is the ruler of this continent.
  • He is a former human and hero before becoming a Demi-God in the web novel.
  • His age is unknown, but he is estimated to be over 300 years old.



About 300 years ago, Leon came to the world where Rimuru and the others currently live. He was 10 years old at that time, but he already found someone he had to protect when he was summoned. This was the girl who fell along with him; a girl named Chloe O’ Bell.

Hence, as his body was being destroyed, he was able to suppress the rampaging magic by sheer willpower alone. This earned him the skill Guardian.” However, as his power was starting to awaken, the young girl, Chloe suddenly vanished. And so, he began his journey of finding Chloe. [ch130]




Chloe Aubert

Due to his cynical personality, he rarely thinks about major alliances with other major parties. Besides, his focus was a straightforward and single goal, to reunite with his childhood friend, Chloe. However, his journey definitely affiliated him with other groups of people [ch131].

El dorado

EL Dorado

As his influence and name spread throughout the people, he was nicknamed the “Platinum Devil.” This is the time where he was gathering subordinates to find his lost friend [ch131].

Moreover, he found a continent and built it as “El Dorado” where is now affiliated with the people on it, as he realized the responsibilities of being a leader [ch210]. Even though it was mainly influenced by Chloe initially [ch131].

Tempest Jura Federation

Tempest Jura Federation

He later met Rimuru and became affiliated with him after having a lengthy discussion with him about his past and current status [ch131].



Chloe Aubert

A very close childhood friend of Leon. They were both summoned into another world together and separated, leaving Leon to find her. She was someone he loved as a sister. Leon’s coolness always fades whenever he is with her and his dedication to spoil her is on a great level.



He isn’t on good terms with Ramiris. Upon meeting, he always wanted to exterminate her a couple of times.

Rimuru Tempest

Rimuru Tempest

They were not on good terms with each other initially, mainly because of how Shizue supposedly was treated by Leon. However, after clearing up the misunderstanding, they were able to be cooperative with one another. Going as far as trusting Rimuru, to take care of Chloe for him.

During one of the latest wars, he evolved into a Demi-God through the help of Rimuru reconstructing his core in order to revive him.

Shizue Izawa

Shizue Izawa

He summoned Shizue by mistake while trying to summon Chloe. He gave her the spirit, Ifrit, in order to save her.

Guy Crimson

Guy Crimson

Leon considers him a good friend, despite certain occasions where he makes advances to him.


Alrose & Claude

 They are the subordinates of  Leon.


Leon Cromwell

As soon as his childhood friend disappeared, he began looking for her. He started a journey to find her and despite the passing years, Leon never ever gave up the search. After a long time of searching, he even considered the possibility that Chloe was already back in the world where they came from. However, since Chloe had no relatives, no one would be able to protect her [ch130].

Hence, Leon decided to learn a summoning spell. With his exceptional intelligence as a hero, he was able to learn different types of magic at a very fast pace, all for just a single girl [ch130].

However, his plan ended up in failure [ch130].

Though, this never stopped his burning desire to find Chloe. As his number of subordinates grew, he obtained the nickname ofPlatinum Devil.” And he continuously spread out his followers in search of the girl [ch130].

As time passes by, he discovers a new continent; naming and building it as the current “El Dorado.” This was also the time that he was driving back the forces of Kazaream. At the same time, he fought Yuuki, while ridiculing him for being naïve [ch210].

Shizue Izawa summon

After taking over the Kazaream castle and studying there, he summoned an Otherworlder that would be later named Shizue Izawa. He gave her the high-ranking spirit, Ifrit, for her to survive. However, before he could do anything more, he was informed that the hero would be coming [ch210].

He left the castle immediately, leaving Shizue in the care of the hero. Unfortunately for him, this hero was Chloe [ch210].

Voice Actors

Japanese – Jun Fukuyama

English – Christopher Wehkamp

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demon lord Leon

I know this character is going to win the hearts of many people out there. He’s truly a badass, and I hope you guys enjoyed reading this blog! Let us know in the comments that what did we miss?! 


1. Reincarnated As A Slime Manga: Chapter 70 

2. Reincarnated As A Slime Manga: Chapter 147

3. Reincarnated As A Slime Manga: Chapter 133

4. Reincarnated As A Slime Manga: Chapter 134

5. Reincarnated As A Slime Manga: Chapter 135

6. Reincarnated As A Slime Manga: Chapter 203

7. Reincarnated As A Slime Manga: Chapter 130 

8. Reincarnated As A Slime Manga: Chapter 132

9. Reincarnated As A Slime Manga: Chapter 66

10. Reincarnated As A Slime Manga: Chapter 133

11. Reincarnated As A Slime Manga: Chapter 134

12. Reincarnated As A Slime Manga: Chapter 210 

13. Reincarnated As A Slime Manga: Chapter 131

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