Strongest Demon Lords Ranked in That Time I Got Reincarnated as a Slime (2026 Update)

 

Introduction — Who Truly Reigns Supreme?

Who truly reigns supreme among the Octagram? In That Time I Got Reincarnated as a Slime, power scaling grows more complex as Demon Lords evolve and unlock Ultimate Skills.

Power in TenSura is not just raw strength. It depends on magicule reserves, Ultimate Skills, intelligence, and centuries of combat experience. Early on, fans assumed all Demon Lords were equal. However, the Light Novels reveal a massive gap between Demon Lord Seeds and the true elites of the Octagram.

This guide ranks every major Demon Lord based on anime feats and full Light Novel scaling.

For full franchise context, start with the That Time I Got Reincarnated as a Slime Complete Guide 

What Is a Demon Lord in Slime?

In TenSura, the Demon Lord title is both political and biological.

There are two types:

• Demon Lord Seed: Powerful individuals who have not undergone the Harvest Festival.

• True Demon Lord: Beings who evolve after gathering 10,000+ souls, gaining massive power and often an Ultimate Skill.

The Octagram was formed after Clayman’s defeat and consists only of True Demon Lords or equivalent beings.

To see exactly how Rimuru Tempest achieved this level of power, check out our full Rimuru Guide for a complete breakdown of his abilities and evolution.

.Ranking Criteria — How We Scaled the Demon Lords

This ranking is based on:

Existence Value (EP): Magicule reserves
Ultimate Skills: Power and versatility
Light Novel Feats: Canon scaling
Combat History: Battles and results

Light Novel feats are prioritized, so rankings may differ from anime-only views.

Strongest Demon Lords Ranked (10 to 1)

10. Clayman — The Marionette Master

Clayman relied on manipulation rather than strength. He remained a Demon Lord Seed and lacked an Ultimate Skill. Even after a pseudo-awakening, Rimuru defeated him easily.

For full context on Walpurgis and Clayman’s defeat, see our Season 2 Full Recap.

9. Frey — The Sky Queen

Frey stepped down after recognizing the power gap. While fast and skilled, she lacks the power of a True Demon Lord.

8. Carrion — The Beast Master

Carrion excels in physical combat. His Royal Beast Form boosts his stats significantly. He later awakens as a True Demon Lord but still falls short of higher tiers.

7. Ramiris — The Labyrinth Creator

Ramiris controls her Labyrinth completely, including space and resurrection. However, her current form limits her combat ability outside it.

6. Dino — The Sleeping Ruler

Dino possesses dual Ultimate Skills and immense potential. His lazy personality keeps him from ranking higher.

5. Luminous Valentine — The Queen of Nightmares

Luminous uses Asmodeus to control life force, granting regeneration and energy drain. Her power and influence place her in the upper tier.

4. Leon Cromwell — The Platinum Saber

Leon’s Metatron purifies magicules, making him deadly against most opponents. His skill and intelligence secure his position.

For a closer look at how Diablo stacks up against characters like Leon,

check out our Deep Dive on Diablo’s Power Level 

3. Dagruel — The Earthquake Giant

Dagruel is a Titan with immense durability and strength. His resistance to magic makes him extremely difficult to defeat.

2. Guy Crimson — Lord of Darkness

[IMAGE: Guy Crimson throne scene] Alt text: Guy Crimson Lord of Darkness Walpurgis

Guy Crimson possesses Lucifer, allowing him to replicate abilities. His experience makes him the peak of Demon Lord power.

1. Milim Nava — Strongest Original Demon Lord

Milim has the highest raw destructive power. Her Satanael generates near-limitless energy, allowing continuous high output.

Absolute #1 — Rimuru Tempest (Chaos Creator)

Rimuru stands at the top.

• Azathoth grants consumption and creation

• Ciel provides instant analysis

• Turn Null grants primordial energy

By later volumes, Rimuru surpasses Demon Lords entirely and becomes god-like. To see his journey and transformations in action, watch That Time I Got Reincarnated as a Slime Season 3, where these powers are showcased in the anime.

Anime vs. Light Novel — Power Scaling Gap

In the anime, Rimuru would struggle against Guy and Milim.
In the Light Novel, advanced abilities and Ciel elevate him far beyond them.

Final Ranking Summary Table

Rank	Demon Lord	Species	Power Tier	Key Ability
#1	Rimuru Tempest	Ultimate Slime	God Tier	Azathoth — Void God
#2	Milim Nava	Dragonoid	Catastrophe	Satanael — Infinite Magic
#3	Guy Crimson	Primordial Daemon	Catastrophe	Lucifer — Skill Copy
#4	Dagruel	Titan	Catastrophe	Magic Immunity
#5	Leon Cromwell	Ex-Hero	Disaster+	Metatron — Purity
#6	Luminous Valentine	Vampire	Disaster+	Asmodeus — Life/Death
#7	Dino	Fallen Angel	Disaster+	Dual Ultimate Skills
#8	Ramiris	Fairy	Variable	Labyrinth Creation
#9	Carrion	Beastman	Disaster	Royal Beast Form
#10	Clayman	Undead Elf	Hazard	Marionette Control

FAQs — Demon Lord Power Scaling Answered

Q1: Who is the strongest Demon Lord in That Time I Got Reincarnated as a Slime? By the end of the Light Novels, Rimuru Tempest is the strongest being.

Q2: Is Rimuru stronger than Guy Crimson in the anime? In the anime, no. In the Light Novel, yes.

Q3: Who is the strongest original Demon Lord in Slime? Milim has the highest raw power; Guy has the most experience.

Q4: Is Milim stronger than Rimuru Tempest? Early on, yes. Later, Rimuru surpasses her.

Q5: How many Demon Lords are in the Octagram? Eight members after Clayman’s defeat.

Q6: What is the difference between a True Demon Lord and a Demon Lord Seed? A True Demon Lord evolves via the Harvest Festival and gains massive power.

Q7: Is Clayman a True Demon Lord? No, he remained a Demon Lord Seed.

Q8: Where does Diablo rank among Demon Lord-level characters? Diablo is not in the Octagram but is extremely powerful.

Q9: Does Carrion become a True Demon Lord? Yes, in the Light Novel.

Q10: What is Rimuru’s strongest form in the Light Novel? Azathoth + Ciel + Turn Null, making him god-like.

Conclusion

The Demon Lord hierarchy shows how extreme TenSura’s scaling becomes. While early villains like Clayman seem strong, the true elites—Guy, Milim, and Rimuru—operate on a near-divine level.

As future seasons adapt deeper arcs, this power gap will become even clearer for anime-only fans.