Great Mothers' Fortress
The Great Mothers' Fortress, serving as the power center for the Dathmiri witches known as the Great Mothers, was constructed within a mountain located on the extragalactic planet of Peridea. This fortress featured a subterranean temple and a soaring spire, the peak of which was adorned with a circular henge. Furthermore, it functioned as the operational headquarters for Grand Admiral Mitth'raw'nuruodo's departure from Peridea. Thrawn ultimately destroyed it in an attempt to impede the pursuing Jedi.
History
Thrawn's alliance
The Great Mothers' Fortress functioned as the dwelling for the witches Klothow, Aktropaw, and Lakesis, who are the Great Mothers of Peridea. Subsequently, Grand Admiral Mitth'raw'nuruodo discovered the fortress and awakened the residing mothers, following his banishment from his home galaxy during the Liberation of Lothal. He then formed an alliance with them, leveraging their magick to repair his Star Destroyer, designated the Chimaera, and to establish contact with one of his agents situated in the primary galaxy. In exchange, Thrawn agreed to transport the mothers and their accompanying cargo with him.
Escape from Peridea
After traversing extragalactic hyperspace, Morgan Elsbeth, Thrawn's agent, arrived above Peridea aboard the Eye of Sion, with the intention of transporting Thrawn and the Great Mothers to Dathomir. She and her hired soldiers arrived at the fortress and were greeted by the mothers. Shortly thereafter, the Chimaera docked above the fortress and began the process of transferring the cargo on board. From this location, Thrawn masterminded the scheme to employ Sabine Wren in locating and assassinating Ezra Bridger, as well as the interception of Ahsoka Tano. Despite the Jedi's survival, the cargo transfer was successfully executed, and preparations for departure commenced. Tano, Wren, and Bridger infiltrated the fortress with the aim of preventing their escape, but Morgan remained behind to provide Thrawn and the Mothers with additional time, sufficient for their exit from the fortress.
Destruction
Seeking to impede the Jedi's progress, Thrawn commanded the Chimaera's turbolasers to bombard the fortress, a decision that visibly displeased the Great Mothers. Tano and Wren narrowly escaped, but the resurrected Night Troopers were annihilated as the fortress collapsed.