#an understatement

As to his current position, 5e’s Sword Coast Adventurer’s Guide features Asmodeus among the list of gods, naming him the “god of indulgence”, and crediting to him the domains of knowledge and trickery. His symbol is “three inverted triangles arranged in a long triangle”, as seen in the image below.² 

While his active circle of worshippers remains small, he is one of the gods habitually turned to by those in need, particularly those who have done something to earn them the displeasure of another god:

After transgressing against a god in some way, a person prays to Asmodeus for something to provide respite during the long wait. Asmodeus is known to grant people what they wish, and thus people pray for all the delights and distractions they desire most from life. Those who transgress in great ways often ask Asmodeus to hide their sins from the gods, and priests say that he will do so, but with a price after death.³

Asmodeus is particularly appealing to those who fear what awaits them after death, or have arrived to find the reality does not match their hopes. For these souls, even the hazards of Baator might be preferable to long centuries of solitary wandering on the Fugue Plane. 

All souls wait on the Fugue Plane for a deity's pleasure, which determines where a soul will spend the rest of eternity. Those who lived their lives most in keeping with a deity's outlook are taken first. Others, who have transgressed in the eyes of their favored god or have not followed any particular ethos, might wait centuries before Kelemvor judges where they go. People who fear such a fate can pray to Asmodeus, his priests say, and in return a devil will grant a waiting soul some comfort.³

The worship of Asmodeus attracts staunch individualists, who desire a future unaligned with the domain of any of the other gods, and are willing to choose self-determination in any form that might approach them.

The faithful of Asmodeus acknowledge that devils offer their worshipers a path that's not for everyone — just as eternally basking in the light of Lathander or endlessly swinging a hammer in the mines of Moradin might not be for everyone. Those who serve Asmodeus in life hope to be summoned out of the moaning masses of the Fugue Plane after death. They yearn for the chance to master their own fates, with all of eternity to achieve their goals.³

Asmodeus achieved his current official status of godhood during the Spellplague, which lasted from 1385 to 1395 DR. After this, for reasons he has unsurprisingly chosen not to reveal, he performed a ritual to alter the metaphysical categorization of all existing tieflings, giving them features that highlighted this connection.

Due to this shift, tieflings are often perceived with wariness by those who believe that Asmodeus is able to exert control over these newly-determined “descendants” of his. While this is an unwarranted suspicion, as tieflings are no more bound to his will than any other individual of another race, the mistrust remains unfortunately pervasive.⁴ 

The true origins of Asmodeus, particularly from 3rd Edition on, are kept rather ambiguous, seemingly quite by design. This is both for Watsonian reasons – that a supreme being of evil such as Asmodeus would not carelessly leave information about his origins (and, potentially, weaknesses) floating around – as well as Doylist: it is a more elegant solution than eternal retcons, and leaves it up to the individual scholar or DM which explanation they ascribe the most veracity to.⁵ 

On the charge of Asmodeus’s true form being a giant serpent, we have Chris Pramas to thank for that bit of lore, stated in 2e’s 1999 Guide to Hell, but rarely mentioned - and not in any definitive manner - from 3e onward.⁶ 3e’s Manual of the Planes, published in 2001, does reference this account, but as a whispered and shadowy theory about the Archdevil Supreme, rather than objective truth.

Brutally repressed rumors suggest that there is more to Asmodeus than he admits. The story goes that the true form of Asmodeus actually resides in the deepest rift of Nessus called the Serpent’s Coil. The shape seen by all the other devils of the Nine Hells in the fortress of Malsheem is actually a highly advanced use of the project image spell or an avatar of some sort. ... From where fell Asmodeus? Was he once a greater deity cast down from Elysium or Celestia, or is he older yet, as the rumor hints? Perhaps he represents some fundamental entity whose mere existence pulls the multiverse into its current configuration. Nobody who tells the story of Asmodeus’s “true” form lives more than 24 hours after repeating it aloud. But dusty scrolls in hard-to-reach libraries (such as Demogorgon’s citadel in the Abyss) yet record this knowledge. Unless it is pure fancy, of course.⁷ 

One can see from the framing of the above excerpt that there is no attempt made at certainty. Perhaps it is mere conjecture, or perhaps a secret, hidden truth that few may know. It is impossible to say for certain. 

Another story of Asmodeus’s possible origin is found in 3e’s Fiendish Codex II. This text, again, does not frame the information given as universal truth, but rather takes pains to emphasize its ambiguity. 

The best way to understand devils and their ways is to listen to the stories they tell about themselves. The most famous of these tales have propagated as myths throughout all the worlds of the Material Plane, becoming familiar to mortals of all sorts. But as is often the case with legends, contradictions abound. For example, the tale of the Pact Primeval is the accepted version of the multiverse’s creation. But an alternate story claims Asmodeus as the fallen creator of the universe.  Countless cultures have their own versions of the Pact Primeval legend. The names of the deities featured in it change depending on where it is told, but the names of the devils are always the same. Perhaps this fact is what inspired Philogestes, the accursed philosopher of evil, to pen his famous proverb: “The gods exist in multiplicity, but Asmodeus is unique.” As is the case with any myth worthy of the name, the following tale is true — whether or not it actually happened.⁸ 

In this account, Asmodeus began as a celestial embodiment of law, formed from the concept itself to fight against the embodiment of chaos — demons.⁹ Over time, as he and his followers became more akin to the enemies they were facing, those celestial beings not engaged in the fight grew leery of what they were becoming, and took him to trial, to account for himself. The god of valor spoke first, laying out the concerns of those gathered against Asmodeus. In response: 

Asmodeus smiled, and the smoke of a thousand battlefields rose from his lips. “As Lord of Battle,” he pointed out, “you should know better than any that war is a dirty business. We have blackened ourselves so that you can remain golden. We have upheld the laws, not broken them. Therefore, you may not cast us out.”⁸

Despite their efforts, the gods were able to find no laws that Asmodeus had broken. Unsurprisingly, as he himself had helped write them. This conflict between Asmodeus and his host and the remainder of the unsullied gods continued on, with the gods unable to get rid of him, and free themselves of the constant reminder of the Blood War.

With time, the concepts of “good” and “evil” entered the world alongside law and chaos, and Asmodeus was able to argue for dominion over those souls that chose evil. The gods loathed the reminders of this fact, however, and when Asmodeus volunteered to move to the empty plain of Baator, they enthusiastically agreed. It was only years later, when the number of souls arriving at their own planes after death began to sharply decrease, that they thought to travel to Baator themselves, where they found a robust operation based around encouraging mortal souls to take to the path of evil. 

“You have granted us the power to harvest souls,” replied Asmodeus. “To build our Hell and gird our might for the task set before us, we naturally had to find ways to improve our yield.” The war deity drew forth his longsword of crackling lightning. “It is your job to punish transgressions, not to encourage them!” he cried.  Asmodeus smiled, and a venomous moth flew out from between his sharpened teeth. “Read the fine print,” he replied.⁸ 

While the recorded story implies a simple act of one-upmanship, a later section of the Fiendish Codex tells us that Asmodeus’s split from the other celestial deities was not so amicable. 

Once he had committed himself to residing in Baator, the deities physically cast him out of the upper realms, and he fell — and fell, and fell. Upon reaching the plain of Baator, he plunged through the nascent layers he had begun to shape. (In some versions, his fall created the layers, breaking the formerly featureless plain into nine pieces, which then arranged themselves into floating tiers.) At last he hit solid ground but continued to fall, spiraling through rock and soil. The protesting earth of Baator tore at his flesh, opening scores of gaping wounds. Still he fell, until he could fall no farther. The point where he finally stopped was the deepest part of Baator — the Pit.  The wounds that Asmodeus suffered in his dramatic fall have never healed. Though he manages to appear blithely unperturbed by his injuries, they still weep blood every day, and he has been wracked by constant pain for millennia.¹⁰ 

This casting down and its associated injuries is corroborated in other texts as well, including 3e’s Manual of the Planes. 

5e’s Mordenkainen’s Tome of Foes seemingly follows on from the Fiendish Codex’s account, sharing one conception of the fallout of Asmodeus’s stratagem, positioned as an in-universe account penned by the aasimar bard Anodius in a work titled “The Trial of Asmodeus”.

At some point after Asmodeus broke from Celestia to rule Baator, he was brought up on trial for unspecified crimes and trespasses. Asmodeus claimed the right to speak in his own defense, and a court was gathered, arbitrated by Primus, a being intrinsically aligned with Neutrality and Law. From Asmodeus’s recorded arguments in his own defense, we can surmise that those on Celestia had accused him of acting outside of the law in actively working to turn mortals to evil. 

The case stretched on, with neither side ceding ground, for weeks, until finally Primus declared his judgment. While Asmodeus could not be convicted of any true crime – for he had acted within the law in all things – he was to take an artifact, the Ruby Rod that is synonymous with his position, which would “guarantee his adherence to law”.¹¹ A quote from Anodius’s in-universe text is helpfully provided by Mordenkainen: 

“I literally sit beneath eight tiers of scheming, ambitious entities that represent primal law suffused with evil. The path from this realm leads to an infinite pit of chaos and evil. Now, tell me again how you and your ilk are the victims in this eternal struggle.” – Asmodeus addresses the celestial jury, from The Trial of Asmodeus¹¹

In a manner similar to his contested origin, Asmodeus’s appearance is described in several varying ways — a fact that seems in line for a principal schemer such as himself. This seeming discrepancy could also speak to varying uses of aspects or projection spells.

The Fiendish Codex II in one instance paints him as “a horned, red-skinned humanoid with a tall, lithe frame” who “dresses in splendid robes and understated but elegant accoutrements.”¹⁰ A later section in the Codex corresponds to this description given in the Book of Vile Darkness: 

Asmodeus stands just over 13 feet tall, with lustrous dark skin and dark hair. He is handsome in the same way that a thunderstorm is beautiful. His red eyes shine with the power of hell, and his head is crowned with a pair of small, dark red horns. He dresses in finery of red and black; a single garment of his might cost what an entire nation spends in a year. Of course, he is never without his Ruby Rod, an ornate piece of unparalleled jeweled finery and vast magical power.¹ 

Regarding his personality, he is most often described as “a soft-spoken, articulate, chillingly reasonable fellow who is confident in his status as one of the multiverse’s most powerful entities. Even when surprised, he reacts with supreme poise, as if he were already three steps ahead of his adversaries.”¹⁰ The Book of Vile Darkness notes correspondingly that: 

The actions of Asmodeus are often mysterious to outside observers, but that is due to the short-sighted and dim-witted view most beings have. Asmodeus’s manipulations are labyrinthine and insidious. They work on a grand scale, although when it suits his needs he is willing to focus his attention even on the status of a lowly mortal soul.¹

¹ Book of Vile Darkness. 2002. p. 165-6.

² Sword Coast Adventurer’s Guide. 2015. p. 21.

³ Sword Coast Adventurer’s Guide. 2015. p. 24.

⁴ Sword Coast Adventurer’s Guide. 2015. p. 118. 

⁵ “Watsonian vs. Doylist”. Fanlore.org. 

⁶ In general, I try to stay in-universe with these lore writeups, but in this case it did feel like some out-of-universe context was necessary. 

⁷ Manual of the Planes. 2001. p. 123.

⁸ Fiendish Codex II: Tyrants of the Nine Hells. 2006. p. 4-5.

⁹ While the description of these events found within the Fiendish Codex is too long to transcribe here in its entirety, I highly encourage you to read the full account for yourself. 

¹⁰ Fiendish Codex II. 2006. p. 73-4.