Sissiri

Sissiri was an ancient Sith Lord whose likeness was chiseled into the rock walls of the citadel on Exegol by 35 ABY. When Supreme Leader of the First Order and Master of the Knights of Ren Kylo Ren arrived on Exegol to confront Darth Sidious, he traveled through the Sith Citadel and recognized a number of statues of Sith Lords that were carved into the walls from his studies.

Of those he recognized were Locphet, Mindran, Felkor, Naga Sadow, and Sissiri. While there, Kylo Ren also heard their unintelligible whispers, along with the familiar voice of Sidious, which he had heard since childhood.

Text and facts from the “Sissiri” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.