The Stone Prison, a clandestine prison, lay far beneath the Royal Manse on the planet of Doan. Its design incorporated multiple levels and a complex labyrinth of corridors, rendering escape virtually impossible. A control room was also present, enabling a self-destruct sequence to be initiated, triggering a series of explosions that would cause the prison's complete collapse. Only the royal family possessed the code necessary to activate this detonation.
Sometime after the conclusion of the New Sith Wars, the Doan Royal Family ceased using the prison. Nevertheless, Prince Gerran was privy to the self-destruction code, which he shared with his wife, Princess Serra. Following Gerran's assassination and the subsequent massacre targeting several mining caste leaders and Jedi Knight Medd Tandar, Serra journeyed to the Jedi Temple on Coruscant. There, she discovered that her father, Caleb, had been killed ten years previously by a Sith Lord. Mistakenly identifying Darth Bane as the responsible party, she contracted the Huntress to capture him.
Serra then secretly reopened the Stone Prison and imprisoned Bane within its walls. She systematically incapacitated and tortured him through various injections. During her interrogations, Bane maintained his innocence regarding Caleb's death. Serra's bodyguard, Lucia—a former member of the Gloom Walkers under Bane's command during the New Sith Wars—was deeply disturbed by Serra's thirst for revenge. Recalling the numerous instances where Bane had saved the lives of the Gloom Walkers, she resolved to repay her debt by freeing him. However, upon his escape, Bane pursued Serra, intending to kill her. Lucia confronted him, but Bane's apprentice, Darth Zannah, arrived at the prison and attacked them, instantly killing Lucia.
In addition to Zannah's arrival, the Dark Jedi named Set Harth also appeared as Zannah's apprentice. However, he later found the Sith holocron of Darth Andeddu and abandoned Zannah to retrieve it from Serra's office. As Zannah and Bane fought in a duel for the title of Dark Lord of the Sith, Serra discovered her dead friend and understood that her quest for vengeance had been misguided. The Princess ultimately decided to trigger the prison's collapse in an attempt to eliminate both Sith. She then escaped Doan, aware that the prison's destruction would be felt in the Royal Manse. Nevertheless, Bane, Zannah, Set, and the Huntress all managed to escape before the prison's destruction, and the Huntress—adopting the name Darth Cognus—submitted to Bane's teachings. Aboard the Stalker, Cognus' shuttle, the two Sith tracked Serra to Ambria, where Cognus killed the Princess. In the shuttle he used to escape, Set began training with his newly acquired holocron, intending to learn the secret of Essence Transfer in order to prolong his life.