The announcement of Rimuru's ascension to a True Demon Lord—following the annihilation of the Farmus army—forced the hand of the existing Demon Lords.
The formal, highly ceremonial invitation to Walpurgis (The Demon Lords' Banquet) arrived shortly after, personally delivered by one of Demon Lord Guy Crimson's subordinates.
This was not a celebratory dinner; it was a political trap orchestrated by Demon Lord Clayman, who intended to have Rimuru denounced as a chaotic threat and eliminated before she could solidify her power.
Rimuru, still adjusting to the immense power of her evolution, was anxious.
Arthur immediately took on the role of her Chief Strategist and Political Guarantor.
"Walpurgis is a stage, not a battlefield,"
Arthur instructed, outlining their plan.
"Clayman's only weapon is deception and manipulation. Our weapon is the absolute truth and the absolute power standing behind it. We will not fight the Demon Lords; we will force them to judge Clayman."
Arthur's plan was twofold:
Rimuru would present irrefutable evidence—gleaned from the captured Farmus agents and her own skills—that Clayman orchestrated the Orc Disaster, the Kingdom of Farmus Invasion, and was manipulating the current political structure.
Arthur's presence, radiating the calm, immense aura of a True Dragon and the Magicule Breeder Reactor, would serve as the non-negotiable proof that Rimuru was not an upstart, but a formidable sovereign backed by a world-ending force.
The journey to Walpurgis was a period of high stress, which further intensified the relationships among the core group.
Rimuru's reliance on Arthur became absolute.
She needed his clarity and immense stability to manage the complex Demon Lord politics.
Arthur, in turn, allowed his sense of duty to merge entirely with his affection for her.
He stood as her impenetrable shield against the entire world.
"I am afraid, Arthur,"
Rimuru admitted telepathically on the final leg of the journey.
"This is much bigger than the Jura Forest. What if they all turn on us?"
"Then I will remind them why a True Dragon guarantees your seat,"
Arthur reassured her, his presence a mountain of calm next to her.
"But they won't. They are political animals. They will respect the order we bring. Focus on the truth, Rimuru. You are the leader. I am just the pillar."
Rimuru allowed Shuna (for magical support) and Shion (as the single, most devoted bodyguard) to accompany them, though they were forced to wait outside the actual summit.
The Oni's anxiety over Arthur and Rimuru entering the den of Demon Lords was palpable.
Shion's protective instinct was nearly violent, while Shuna meticulously prepared every anti-demon ward and emergency spell she knew, based on the theories Arthur had shared with her.
Before the gate, Shion bowed low to Arthur, her eyes burning with fierce loyalty.
"Arthur-sama, if they touch our Queen, I trust you to leave nothing of that place but ash. Do not hesitate."
At Walpurgis, the atmosphere was thick with hostility.
Clayman immediately launched his attack, lying to the assembled Demon Lords and attempting to frame Rimuru as a violent chaos-bringer.
Rimuru, guided by Arthur's subtle cues and strategic planning, countered every lie with undeniable truth.
She presented evidence of Clayman's various manipulations—from manipulating the Orc Lord Geld to orchestrating the attack by the Kingdom of Farmus.
The sight of the newly ascended True Demon Lord Rimuru standing resolute, with the imposing figure of the Dragon Guardian Arthur at her side, was enough to sway the political calculation of the other Demon Lords.
When Clayman's lies were fully exposed, the confrontation turned physical.
Clayman revealed his true, desperate strength, but it was no match for the might of a True Demon Lord.
Rimuru, with a terrifying, absolute display of her new power, eliminated Clayman.
With Clayman destroyed, Rimuru's place among the Demon Lords was immediately secured.
She had survived her first major political test and secured the safety of the Jura Tempest Federation from the Demon Lord faction.