https://www.dndbeyond.com/monsters/lady-illmarrow

Lady Illmarrow is a legend — an ancient lich said to dwell in a castle of bone and ice in the coldest regions of the Lhazaar Principalities. Some stories say that she is served by a legion of undead and that she maintains a court of vampires and ghosts in her palace of ice. Other tales claim that when anyone dies in Lhazaar, Illmarrow chooses whether to take their soul before it passes on to the Keeper and Dolurrh.

But Lady Illmarrow is no folk tale. She is the greatest necromancer in Eberron, and after centuries of silence, she is setting ancient plots into motion at last. She is the power behind the Order of the Emerald Claw, but her motives for founding the order are buried in her past. Lady Illmarrow has no interest in ruling the living. Rather, she seeks to become Queen of the Dead.