Korelei was a female Keshiri Lord of the Lost Tribe of Sith who became one of the final host bodies of Abeloth and was killed at the New Jedi Temple when Abeloth and the Lost Tribe of Sith were defeated.
The Lost Tribe of Sith kinda have their whole deal in their name, but when you find out who "Abeloth" is it's just. Wtf were they doing in Legends lmao