Hadar

Hadar, also known as the Dark Hunger, was an Elder Evil from the Far Realm who had taken possession of one of the stars of Realmspace. Unlike normal stars, Hadar didn't have a fixed place in the sky but instead danced and wavered across Realmspace.

Description
Hadar was a cinder-red star, barely visible in the night sky.

History
Hadar and the other Far Realm-infested stars of Realmspace were somehow related to the Eldest.

Hadar was a dying star, slowly burning into annihilation. Because of that it sent its agents, the Heralds of Hadar, to Toril to feed on living creatures in a desperate attempt to avert its demise.

Hadar was usually sought out by some warlocks to make a pact with it. To those few Hadar bestowed the ability to use the Arms of Hadar spell.