Astaroth

Astaroth was a demon prince of the Infinite Layers of the Abyss,   His title was Diabolus and he was concerned with matters of prophecy. After his death, "Astaroth" became an alias for the arch-devil turned god Gargauth. The original Astaroth became a vestige.

History
Some time in ancient history, Astaroth—even then a very powerful demon lord—volunteered to fight beside the Queen of Chaos against the Wind Dukes of Aaqa, but she rejected him.

Early in the Blood War, Astaroth infiltrated the ranks of the devils, even achieving the post of Treasurer of Hell. His espionage grievously sabotaged the devils' war effort, stopping them from winning any decisive victory against the demon hordes. For this, he earned the name "Diabolus". Finally, however, the arch-devil Gargauth discovered Astaroth's true nature and exposed him. Astaroth escaped Asmodeus's rage and retreated to his dwelling place in the Abyss. Gargauth became Treasurer of Hell himself.

To guard against the revenge of the Lords of the Nine Hells, Astaroth laid plans. He made a bargain with fellow demon lord Ahazu that, in the event of his death, his body would be imprisoned in the Wells of Darkness in the Abyss, in order that he might be resurrected. He also used his prophetic powers to establish cults devoted to him among mortals on uncounted worlds. His aim was no less than to ascend as a god. He even succeeded, after a fashion, but it was not enough to escape the Hells' vengeance. Nor did his prophecy warn him of his doom. In the end, Astaroth was killed in terrific battle by Gargauth during his own wanderings as an exile of the Nine Hells, at the command of Asmodeus. The Abyss itself tried to resurrect Astaroth in his assigned pit in the Wells of Darkness, but Gargauth ignited permanent hell-fire there, so Astaroth's body constantly burned even as it reformed.

Thereafter, Astaroth was presumed deceased, at least to other fiends. Nevertheless, not dead but not living, some essence of Astaroth lingered in the form of a vestige, only reachable by pact magic. It was even whispered that the demon lord remained alive but sleeping, within a temple dedicated to him on Toril. This account went on to warn that Astaroth still sought to "poison the words" of those who entered imprudently.

Meanwhile, Gargauth took Astaroth's name as his alias and stole the worship of his few surviving cultists on Toril, thus receiving his first taste of godhood. He maintained these cults in Astaroth's name.

In the mid–14 century DR, a cadre of demon-spawned tieflings arose in the former lands of Narfell. Naming themselves the Scions of Astaroth, or "Astarothans", after the long-dead demon lord, they viewed Faerûn as another front in the Blood War. Ironically, they set themselves against the Knights of the Shield, a group that unwittingly served Gargauth.

Circa 1374 DR, an Olin Gisir of the North named Meraera and her party explored the ruins of the temple to Astaroth. Meraera warned her companions to be silent, and claimed to be prepared with just the spells to keep Astaroth in his slumber.

Personality
More than other demons, Astaroth had a deep, undying hatred of devils and sought vengeance against them.

Powers
Astaroth had a gift for prophecy.

Realm
Though he ruled no abyssal layer of his own, Astaroth dwelled in a layer filled with steam and floating chunks of burning stone.

Relations
Helanna Darkstorm, a leader of the Knights of the Shield around 1370 DR, was once a consort of Astaroth.

Summoning
A wielder of pact magic like a binder could summon the vestige of Astaroth and gain powers thereby. His seal had to be drawn on stone that had recently been burned then doused with cold water. He manifested in a cloud of steam from the seal, condensing into the visage of a handsome human with draconic and feather wings, with flicking serpentine tongue. He appeared nervous. His body was forever being slowly consumed by hellfire.

A binder who bound and made a pact with Astaroth exuded a stink of brimstone and their eyes were covered by a cloudy film. In manner, they became morose and fatalistic, thanks to a vague but unshakeable feeling of impending doom. Astaroth demanded they attack devils whenever the opportunity occurred. In return, Astaroth bestowed several powers. One was to see into the future, as with the divination spell. Another was the ability to pass among fiends of all kinds, with skill in deceit and disguise. The binder could also wound creatures that could only be harmed by silver, like many devils. Finally, they could burn with black Abyssal flame: all magical flame they produced turned vile, and the binder could hurl a fireball of this kind thrice a day.

The False Astaroth
After slaying the demon lord, Gargauth used "Astaroth" as an alias for his misdeeds. For example, in the dwarven legend titled "The Legacy of Astaroth", Gargauth adopted the guise of a dwarf minstrel named Astaroth to corrupt a hall of greedy dwarves and lead them to their doom. Gargauth provided the spell Astaroth's augmentation to priests of other gods who unwisely called upon him.

Background
Astaroth is based on the Astaroth of real-world medieval demonology, upon which the pact magic of the 3.5-edition Tome of Magic is closely based.

The D&D Astaroth first appeared as just a name in a list of high-ranking demons in the 1st-edition Monster Manual II. Later Realms sources established Astaroth had been slain and replaced by Gargauth. However, for a third Astaroth, the "Urban Magic" Web Enhancement for Cityscape presents a fallen angel turned vestige for pact magic named Astaroth the Unjustly Fallen. However, this Astaroth never became a fiend, had no apparent interest in prophecy, and died at mortal hands, so it is unlikely to be the same entity as the demon lord Astaroth. (There is also no evidence for Astaroth the Unjustly Fallen existing in the Realms, except in hypothetical vestige form for use by binders.)

This was confirmed in the "Savage Tidings: Gazing into the Abyss" article in Dragon #357, which introduces a second vestige named Astaroth and expands the story of the original demon lord.