Red Wizards of Thay
Necromancers, dark priests, sorcerors, warlocks and wizards notorious as cruel slavers, demonologists and employing other dangerous arcane experiments. Created an entire nation powered by the undead - many of the rulers being powerful undead themselves: Lich, Vampire, Mummy Lords, etc.
(See also: https://forgottenrealms.fandom.com/wiki/Red_Wizards )
(Considering: https://www.worldanvil.com/w/not-forgotten-realms-palant/a/red-wizards-of-thay-article-1 )