Eiro silently flew through the narrowing mineshaft, taking in the information that his duplicate had just learned. If Nelly was the first Naiad... her and Eiro had to have a conversation about that once she was better again.
Since the Naiad Queen had healed her physical body, Nelly only needed to have the mental strength in order to wake up now, and Eiro knew for sure that she had that strength in her. But, for the time being, since he had the confidence that Nelly would be okay now, Eiro could properly concentrated on what was going on directly around him in the central material plane.
To calm them down as well, Eiro let the others know that Nelly was going to be alright. Of course, particularly Sarius and Gondos were now able to relax considerably as they did their part of Eiro's plan. That being the case, the party finally reached their destination. It was a specific section of that massive demonology sigil, at the center of which the Devil was hidden away.
One of the Devil's powers was the ability to access Hell at any point; this was the main conduit through which the Devil was trying to pull this part of the world into a whole other realm, which was something not usually possible. Usually, demonology was something that allowed for the summoning of individual demons or objects from hell for the means of forming a pact.
Eiro didn't know exactly why pacts and contracts were such a compelling thing to other demons, but he figured that it had something to do with the will and personality of the father of all demonic beings, the Demon King, but he certainly would make use of this fact to the fullest during his plan.
In front of the party, in the middle of this regular mineshaft, was a large, ornate gate that pulled open on its own. Beyond it, the space opened up into a large hall that had been prepared beforehand, where the Devil was currently seated on a throne of distorted, twisted bone.
"I've been awaiting you, little imp," the Devil smiled broadly.
"...Trying to impress us somehow, even though all you've been doing is run away from us this whole time?" Eiro asked with a raised brow, and the Devil's face twisted into one of annoyance.
"I'd better be careful with your words, or else you will regret it," the Devil pointed out, glancing over at Ariella. The concentration of unholy energy in this space was beyond anything else that they had experienced in these hallways. Despite the protective barrier placed around her, she was feeling weaker.
But of course, Eiro could tell that the Devil was specificially focusing that disgusting magic onto her, trying to whittle her down more and more since he 'knew' that she was the biggest danger to him.
"Ariella," Eiro looked over at her, and the nephilim looked back at him, "Are you sure?" she double-checked, and the Demon nodded his head.
Without a moment's hesitation, Ariella forced herself to straighten her back, and her wings' feathers started to let of a deep glow that was actively pushing away that encroaching darkness that the Devil's magic was forcing into her direction.
A Nephilim was, in nature, one of holiness. Her flesh, her blood, her feathers and her hair; everything was deeply instilled with holy energy. However, due to the sins of a nephilim's parent, they required a massive amount of work to actually harvest this energy properly.
Ariella had grown strong enough to do so to a certain degree, but it wasn't enough to fight off against the unholiness of the Devil. But, one of Ariella's abilities counter-acted this quite well. For a limited amount of time, she could unleash all of her holy energy fully, but in return, she wouldn't be able to access it at all for a certain amount of time.
With a vulnerability against unholy magic, but without the holy energy within her to protect her to a certain degree, using this ability would be a sign of certain death. That was why Ariella had entrusted Eiro with the decision of 'when' she was actually allowed to use that ability. That meant that to Eiro, the end of the battle was certain.
The Devil, who knew of the ability that Ariella used, realized this himself. His face twisted away from annoyance into complete anger, "You! You! How dare you, you little-"
As Eiro grasped the Devil's hand, the two spoke in unison, "I pledge on the blood flowing through my veins to follow the rules of combat established."
"Only I, the World, may strike down the Devil, and only the Devil, and if any ally, servant, or otherwise affiliated being dares attack the Devil, may I be struck down."
"Only I, the Devil, may strike down the World, and only the World, and if any ally, servant, or otherwise affiliated being dares attack the World, may I be struck down."
Eiro could feel a deep energy flow through the body of the Devil, but within himself, nothing happened. That was something that didn't get past him either. Confused, the Devil stared at the figure in front of him, "What... what is going on? The pact, your side of it, it..."
"Gondos, Sarius... do it," the Demon spoke with pure disgust at the being in front of him, his voice being carried telepathically to the two contracted spirits. The moment they heard the message, the mineshafts collapsed in waves of fiery molten stone, crushing every last monster and demon under their weight.
The sacrifice of life needed to activate the demonology sigil was gathered all at once, and realizing that something was wrong, the Devil's body disappeared in a wisp of smoke, and the physical contact between the two beings disappeared.
The world shifted, and the fiery unholiness of hell flowed from all directions. The demons in the room were strengthened, and Eiro's party was weakened.
Eiro glared at the Devil, whose face was filled with a panic. Eiro's pact didn't activate. But the Devil's did. The Devil was someone affected by the Demon King's lineage, being a direct descendant.
But Eiro was no longer one such being. He was an Arcanus; demonic in nature, but a unique demon that had no nee to follow the constraints and rules set by and onto the Demon King.
He no longer had a bane in the form of Holy magic, and there was no need for him to adhere to any sort of pact. Sure, even before now, he never felt constrained to do so, but he never formed a direct 'pact' like was attempted just now either.
A pact that did affect the Devil, who now could not escape from this place further than a mile in any direction, and could not attack any members of Eiro's party. He would only be able to attack Eiro. But for Eiro, it didn't matter.
His party could do whatever they wanted, and even if they attacked the Devil, he would be unaffected. It still wouldn't be easy to kill the Devil, a master of unholy magic and demonology.
In the meantime, Eiro was going to take care of some business.
---
[You have entered Hell for the first time]
[In order to allow you to claim your throne as the Lord of the Arcanus, the Demon King calls you for an audience]