You mean the Cult of Forgotten Shadows? The Undead / Priests society? I myself would be more than happy to find one like this, but for some reason Undead guilds and characters are a rare thing here (and a hot topic for arguments, lol)
The guilds from this forum that might suit you are - Veilbound Vigil (💀 Death Knight Roleplay - Veilbound Vigil (Neutral RP) - #50 by Tenasa-argent-dawn)