Gargauth

Gargauth
Broken animal horn
Aliases	Astaroth, Gargoth, the Hidden Lord, the Lord Who Watches, the Lost Lord of the Pit, the Outcast, the Tenth Lord of Nine
Alignment	Lawful Evil
Divine Rank	Demigod / Arch-Devil
Pantheon	Faerûn
Portfolio	Betrayal, Cruelty, Corruption, Power
Domains	Charm, Evil, Law, Trickery
Home Plane	Prime Material Plane
Worshippers	Corrupt politicians, Sorcerers, Traitors
Favoured Weapon	Corruptor (Dagger)

Worshipped by some in Faerun as a demigod of corruption and betrayal, Gargauth is an archdevil who was apparently exiled from Baator because he was too much of a handful for the other Archdukes of Hell, though much of what happened is never actually revealed. He was probably just a casualty of the politics of hell, but rather than being cast down or destroyed, he managed to get out.

Afterwards He travelled the planes, returning to Toril time and time again. He spreads his cults and corruption around, with the aim of ensnaring the planet and dragging it back to the Nine Hells where he can rule it as a Tenth layer, because it worked so well for Mephistopheles when he tried it. Though he is also opposed to other evil deities like Shar and Cyric.

The fact that Gargauth holds some actual divine status shows that he could have been a serious power player in the politics of Hell, since it took Asmodeus so long to attain similar status for himself. Although that also illustrates the point that personal power alone can mean very little on the planes when the Archdukes of the Nine had much more widespread influence and control.

Somehow got trapped in a shield for the events of Descent into Avernus