The Preeminent is a major villain in the fifth season of Ninjago.
Search for the Realm Crystal
She was first mentioned in episode 49 "Peek-A-Boo", during a conversation with Morro and Bansha. She was later seen in "Kingdom Come", when the different realms of the Ninjago universe were being mentioned. It was revealed Morro and his allies Ghoultar, Bansha and Soul Archer are trying to release her because she has been trapped in the Cursed Realm, and she seeks to destroy all realms.
After Morro released her in episode 53 Curseworld Part I It was revealed she is the Cursed Realm itself, and its prisoners are merely trapped in its mouth. She destroys everything in her way except for ghosts. However, Nya unlocked her true potential, using the element of water to drown and killed the Preeminent. This also included all those banished in the Cursed Realm, including the ghosts, the Anacondrai cultists, and Garmadon.