Asmodeus

Asmodeus, the Lord of the Nine Hells is the devil god of the Nine Hells and represents mastery of tyranny and domination. He relishes in corrupting mortal souls with his honeyed words. He rules his domain with iron rule and punishment he inflicts for crossing him are legendary. Devils and other evil entities pay him tribute, while warlocks are drawn to his power.

Appearance
Once a celestial, Asmodeus is depicted in many tomes and murals as a handsome humanoid of deep, red skin and long, black hair with two curling horns rising from his brow.

Relationships
Asmodeus has many enemies even among the Betrayer Gods, many of whom only follow him out of fear. His archenemy, however, is Avandra, the Changebringer, who has exasperated him throughout the ages and defeated him during the Calamity.

Vespin Chloras
The archmage Vespin Chloras released the Betrayer Gods from their planar prisons, seeking their power and guidance. Instead they immediately enslaved him, and he is said to now be a devil serving at the left hand of Asmodeus.

Desirat
Desirat was the companion and mount of Asmodeus during the wars of the Calamity. She was captured and imprisoned beneath Mount Mentiri by the original pre-Divergence Cerberus Assembly and remains there, giving birth to the geo-thermal activity in the area.

History
During the Founding, when demons of the Abyss spilled forth to feast on the mortal victims of the Primordials, many celestials who had battled the demons turned to tyranny and forged new hells under the leadership of Asmodeus, himself a fallen angel; he corrupted these celestials into the first devils.

During the Age of Arcanum, Archmage Vespin Chloras released the Betrayer Gods from their prisons. From their new capital of Ghor Dranas in Wildemount, the Betrayer Gods spread their influence and eventually made an assault on the bastion of Vasselheim. The battle lasted twenty days and nights but, with the divine aid of the Prime Deities, Vasselheim and its inhabitants stood triumphant, if battered, at the end.

The gods prepared for war. The Betrayer Gods each forged a sentient weapon with the life force of a greater fiend: the Arms of the Betrayers. Asmodeus, for his part, forged the Mace of the Black Crown from the life force of an erinyes named Xartaza, who attempts to recruit more souls for Asmodeus by manipulating the wielder. During a brief period of unified interests, Asmodeus and Lolth exalted an immortal assassin, Jourrael, the Inevitable End, who could not be completely destroyed as long as their contract remained intact; several centuries later, Jourrael remained immortal.

One theory on the origin of tieflings is that they were created in Ghor Dranas as a result of some of the city's inhabitants tying their bloodlines to Asmodeus in exchange for magical knowledge.

During the Calamity, Asmodeus deceived and betrayed Sarenrae, and killed most or all of her worshipers, in one stroke.

The original Cerberus Assembly tore Desirat, phoenix mount of Asmodeus, from her master and bound her beneath Mount Mentiri for study.

Avandra defeated Asmodeus during the Calamity by tricking his armies into attacking one another.

Trivia

 * One of the oldest objects in Grog Strongjaw's Bag of Holding was a signet ring with the symbol of Asmodeus, recovered from a "big demon" who had body-slammed him onto a spike. It was used to assert belonging to the cult of Asmodeus. This demon may have been Juurezel, a glabrezu demon who posed as a "devil prince".
 * The adventure hook Twilight Phoenix in the Explorer's Guide to Wildemount involves archmages who worship Asmodeus attempting to free his mount Desirat from her prison.