Shadovar

Shadovar  are sometimes called Netherese, although this isn't strictly accurate.  They are the inhabitants of the city of Thultanthar which spent 1700 years in the Shadow Realm after Karsus' Folly.  It returned to Faerun in 1372 DR.

Early in the Year of Wild Magic, a mysterious flying city of black walls and high spire's materialized above the Dire Wood. Shortly thereafter, it came to rest near the Scimitar Spire mountains in southern Anauroch. Its appearance coincided with the flooding of the Shoal of Thirst. The inhabitants of the newly arrived city are the descendants of Netherese wizards who slipped into the Plane of Shadow to escape the destruction of Netheril . Legions of dark-armored wizard-warriors patrol the city's streets and new surroundings, and a circle of archwizard shades infused with the power of shadowstuff leads the city, just as the Netherese mage-princes ruled these lands in olden times. The city of Shade represents one of the most potent concentrations of arcane might on the face of Toril, and its unexpected arrival troubles the councils of the wise and the powerful across Faerûn.

While they have similar aims, they are rivals of the Neoba'etith as they are chasing the same things

The Shadovar are scouring Faerun for traces of their lost civilization.