Mephistopheles

Cania, like Stygia above it, is a bitterly cold realm of glaciers and howling ice storms. Mephistopheles holds court here with the ice devils that make up his retinue. Operating from his great tower, the icy citadel of Mephistar, he conducts a never-ending series of experiments that expand his understanding of arcane magic and of the planes of existence. Mephistopheles keeps his realm churning with punishing storms. He doesn’t entertain visitors, and Asmodeus has charged him with maintaining a stout security force around Nessus. Travelers that aren’t protected against the environment, which is cold enough to kill a creature in seconds, have little hope of surviving.
The foremost wizard in the Hells, Mephistopheles suffers nothing that would compromise his intellectual focus. He hates distractions and allows only particular devils to speak to him without first being spoken to. He has been known to disintegrate minions for the smallest transgressions, and sometimes carries out an execution simply because he suspected that a devil was about to do something to annoy him.
Mephistopheles is able to devote almost all his time to his research thanks to the loyalty of Hutijin, his top lieutenant. Even though Hutijin commands enough power to threaten his master’s position, he is content to remain at the right hand of the throne, at least for the time being.

Experiments in the Unknown

Cania is essentially an enormous laboratory. Mephistopheles and his devotees prefer to conduct their studies in a wasteland where they can unleash gouts of arcane energy without destroying anything important. Experiments involving new spells, new magic items, and other innovations for the infernal arsenal regularly cause localized cataclysms in this place.
This activity attracts numerous spies despite the inhospitable environment. Merely observing Mephistopheles’s disciples at work can provide insights into the nature of their research and the discoveries they have made. His court is constantly alert for agents from Dis, since it greatly pains Dispater that Mephistopheles might come across a scrap of information that he doesn’t possess. A number of renowned archmages, including Mordenkainen, have at times found their way into this realm on a search for forgotten lore or in the hope of confirming a theory of arcane magic.

Keeper of Arcane Souls

Mephistopheles and his followers specialize in luring wizards and sages into making compacts with the Nine Hells. Of all the Lords of the Nine, he has the lowest quotas but the highest standards. He harvests the souls of skilled wizards and cunning sages, exactly the sort of folk he needs to further his research. Curiosity and ambition are motivating factors that entice such souls into his service — often, a mage who gets an opportunity to join the cause of Mephistopheles sees that invitation as proof of one’s ascension to greatness.
The downside to this arrangement is the true nature of Mephistopheles, which is apparent only after a new contract is signed. He can be charming when he recruits a soul directly, and his agents are careful to avoid making any promises about his actions or attitudes. But once a soul arrives in the Nine Hells to serve him, it invariably faces decades of routine work or tedious study.
Thus, few who join his stable of arcanists remain happy with their decision, but they would be well advised not to show any discontent. Mephistopheles fills his contracts with cleverly worded clauses that allow him to annihilate any of his servants with a word. As further protection against dissent, he isolates his minions, allowing them to gather in small groups only when needed to carry on their work. Even then, the law of Mephistopheles prohibits all but the most vital communication, limited to why they have come together. Some of the most skilled but most gullible former wizards of the Material Plane now toil eternally in Cania, alone except for their books, their tools, and their regrets.

Storehouses of Lore

Libraries and other places where arcane knowledge is recorded or contained are scattered across Cania, mainly to ensure that a single disastrous experiment at one location can’t destroy the evidence of all the work conducted at other sites. In his pursuit of ever more lore, Mephistopheles combines his prodigious intellect with his obsessive nature. This combination of traits enables him to delve far more deeply into a topic than most ordinary wizards can even conceive of. Even the tiniest of trivialities is fascinating to him.
Sometimes, however, the business of the Nine Hells forces him to relinquish direct oversight of a project. When he returns to his research, a new mystery might capture his fancy, while the older project continues to move forward without his oversight or interference.
Here and there, tucked away in Cania’s terrible environment and similarly buried in the immense bureaucracy of the Hells, stand long-isolated citadels occupied by sages and spellcasters toiling away at some seemingly forgotten endeavor. The supervisors of these projects might have achieved incredible results that they patiently wait to share with Mephistopheles the next time his attention points in their direction.

There are few problems that cannot be solved through the application of overwhelming arcane firepower.

— Mephistopheles

Ruler of the 8th Layer of hell - Cania

Aligned Organization

Lord's of the Nine

Devils bargain with mortals to upend the divine order. They stake claims on souls that would otherwise go to the gods or be cast adrift somewhere other than the Nine Hells. If you are already a creature of Law and Evil devoted to no other entity, your damned spirit is of meager value.