One must shed Weakness to reign in Chaos.

The Pantheon of Erethelon
Stewards of the Black Sun
Erethelon, the Prince of Darkness: Erethelon is often merely depicted as his most common sigil: the black sun, a massive ball of dark fire that soaks the land below it in darkness, and clouds out every light whose shadows it touches - however, he normally appears as a pale white and gaunt elvish man, wearing a black cloak over dark-red scaled armor. He is normally depicted in this form as carrying a ring of nine keys in his left hand, and grasping his terrifying cold iron mace, the Final Darkness, in his right. As his brother, Borondor brings the day, it is Erethelon that brings the night. Erethelon is a god of strength, cruelty, and domination, preaching to his followers the annihilation that comes with entropy, and the steps that must be taken to prevent it. Erethelon's pantheon is then structured as the ultimate hierarchy of power, with the greatest brokers answering directly to the prince himself, and all others finding themselves somewhere between there and the bottom. Followers do not merely pray for the intercession of their gods, but they instead barter for power, signing contracts, or make profane offerings to receive a boon. Whether the adherents of the faith adhere out of genuine belief, or sheer ambition, it does not matter. All contracts bartered are done always to the benefit of Hell.
The Nine Hells: Hell is as geographically and politically hierarchical as would be expected of the Prince of Darkness's domain. It is divided into nine separate layers, sometimes called the Archduchies of Hell, each ruled over or stewarded directly by a lesser god. Each layer exhibits extremely different environments, often shaped by their ruler's proclivities or vices, and each is layered below the next, with the Prince's personal domain lying at the very bottom. The Archduchies of hell are Avernus, Dis, Plegestos, Malbolge, Maldomini, Stygia, Erebus, Nocturna, and the Pit. The topmost layers tend to exhibit the most iconic aspects of hell, with lakes of fire, massive volcanoes, and meteor strewn wastelands. As one reaches lower, they find more cities, civilization, and of course, darkness. This culminates in the Pit of Hell, a massive city sitting at the very bottom of the nine layers, where the Prince of Darkness reigns from his Fortress of Shadow.

Barbatos, Keeper of the Keys: The Lord of the First, Barbatos is responsible for overseeing the most common gateways into Hell - he knows the name of all those who enter his domain, and sends his followers to meet with them, and determine whether they should be allowed entry, or residence, in Avernus or beyond. His followers then maintain the portals which allow the particularly lucky to simply pass directly to a lower layer, rather than having to trudge physically downwards. Barbatos is also considered the jailor of hell, often keeping devils who have fallen out of sway with the Prince of Darkness. Rumors swirl around Barbatos's origins, or whether he is even a devil at all - whatever the case, he and his followers are considered strange as diabolists go.

Dispater, the Iron Duke: The Lord of the Second, Dispater is the metaphorical castle of Hell. Forces invading hell in great number, in failing to gain Barbatos's safe passage, will be forced to fight from layer to layer until they reach the Pit. Dispater then maintains the planar trenches which can be empowered during times of invasion, and his lava drenched plane of Dis is filled with layers upon layers of fortresses and defensive networks. Despite the many rivalries of Hell, Dispater is respected for dispatching his engineers to every layer to build fortresses and defenses, and in sending his armies wherever in Hell they are needed. Dispater tolerates and ignores much of the bickering between the Arch-Dukes of Hell, but whenever this behavior drifts to becoming a threat to Hell itself, it draws his ire swiftly.
Moloch, the Diabolist Berserker: The Lord of the Fourth, Moloch is the berserker general, the Arch-Devil tasked with leading Hell's forces in the battle against Borondor and his followers, as well as any other do-gooders who threaten the interests of Hell, such as the hated followers of Ariendale. From his wasteland duchy of Malbolge, a little version of Sorthal's own domain, he drills tens of thousands of devils in never-ending mock battles, which sometimes break into actual fighting. In war, he demands of his soldiers, and his followers in Adra, to completely annihilate their enemies in combat, leaving nothing but smoking entrails in their wake.
Baalzebul, the Lord of Flies: The Lord of the Fifth, Baalzebul was once an angel serving Ariendale, tasked with innovation and ingenuity. What began as innovations to alleviate suffering slowly turned to darker inquiries, and upon being discovered, Baalzebul was cursed by Ariendale to forever be seen as a monster - now a swarm of flies in the shape of a man, Baalzebul is forever pushing the boundaries of knowledge, both magical and mundane. Tasked with churning out the many beasts, weapons, and atrocities of Hell, rumors swarm around the Lord of Flies that he seeks more than to remain simply an Arch-Devil. He is a particularly popular god for seekers of arcane power to form contracts with, if they are willing to suffer the consequences.
Mephistopheles, the Merchant of Souls: The Lord of the Sixth, Mephistopheles is a keeper of contracts and agreements - within the expansive libraries and scriptoriums of his realm of Stygia are stored all of the pacts ever formed to which a devil, diabolic servant, or affiliate of Hell was party. It is within the law courts of Stygia that mortals and devils alike are held to account, in the extremely byzantine, and often cruel, form of diabolic law. This is all done to make sure that those who have formed a pact with Hell keep it, but also to ensure the reputations of devils as *somewhat* trustworthy is maintained. The Merchant of Souls is named such because he enforces the payment of these contracts as well, which often includes the transacting of souls to and from various devils and their mortal clients - and none possesses more mortal souls than he.
Mammon, the Argent Devil: The Lord of the Seventh, Mammon is the banker of the infernal world. The many offerings made to the Arch-Dukes, minor Devils, and Erethelon himself, all go through Mammon before they find their way to their respective targets - and Mammon extracts fees at every turn. Mammon is tasked with safeguarding the immense and resources of Hell, and with investing that wealth in the best devils, the finest servants, and the most important temples. While an unimaginable sum leaves the vaults of Erebus every day, Mammon is no fool, and his greed would put a Red Dragon to shame - for every coin that leaves, two take its place, and Mammon is reported to be the richest being in the universe, bar none.

Tesseriss, Lady of the Night: The Lady of the Eighth, Tesseriss is the Madonna of Darkness and Shadow, whose shroud covers Adra each night. Her followers are the spies, seducers, and influencers of hell, using the baser instincts of Kith and Eldar alike to their advantage, and gathering information across both Hell and Adra. She shares this information with Erethelon freely, and will offer it to the other courts of Hell as well, for a price. Tesseriss's followers are also often the most genuine and fervent in their worship of the Prince of Darkness, attending to the many temples of the faith spread across the planes. Tesseriss herself is famously in love with her Prince, and the two have consorted for eons. It is said that when he becomes a King, she will sit by his side as a Queen of the Night.

Asmodeus, the Enforcer of the Will: The Lord of the Ninth, Asmodeus is the Prince Regent of the Pit, where Erethelon rules over Hell. While Erethelon oversees all of the Nine Hells and beyond, Asmodeus is tasked with the day-to-day business of the Prince's personal domain. Despite having to share his turf with a Greater God, Asmodeus has an outsized influence among the Arch-Dukes, and is considered Erethelon's most loyal and ancient servant, and for this reason, is his enforcer. When the hierarchy of the Nine Hells is threatened by upstarts, or when the direct intercession of the Prince of Hell is required, Asmodeus is sent in his name, acting as his will made manifest. It is the order of the Illriggers, the peacekeepers and troubleshooters of Hell that answer directly to Asmodeus, and when a problem is not worthy of his direct attention, Asmodeus's Illriggers will be sent instead.
Saint Abigor, Patron Devil of Castigation
Saint Agares, Patron Devil of Whips
Saint Andonides, Patron Devil of Liver
Saint Barbas, Patron Devil of Hellhounds
Saint Bifrons, Patron Devil of Imps
Saint Mainard, Patron Devil of Famine
Saint Melchon, Patron Devil of Wolves
Saint Morax, Patron Devil of Landlords
Saint Neabaz, Patron Devil of Paperwork
Saint Nepthit, Patron Devil of Undead
Saint Ordelis, Patron Devil of Eclipses
Saint Stoobin, Patron Devil of Hazing
Saint Zepar, Patron Devil of Lines
Level of Organization: Highly Organized - Arch-Devils each choose Diabolic Receivers to hear and interpret their orders, which they then pass on to their own large groups of followers. The Herald of the Black Sun is the Diabolic Receiver who reports directly to Erethelon, and each Receiver operates semi-independently of each other, with all paying respect to the Herald.
The Pact of Domination: Erethelon's pantheon is in a godpact with Dramirus's pantheon and the demi-god Goretawn.
Friendly Pantheons: Erethelon's pantheon is friendly towards the Pact of Mortality, Sorthal in particular.
Hostile Pantheons: Erethelon's pantheon is hostile towards the Pact of Order, Borondor in particular, the Despised Godpact, Marzedon in particular, and the Defender Godpact.