Battle of San Leor
The battle was waged on the holy Imperial world of San Leor by Sisters of Battle forces under Abbess of the Adepta Sororitas Sabrina. Sabrina and her forces originally traveled to the world for a pilgrimage, but became beset by Daemons, Traitor Guard, and the Alpha Legion. They survived only thanks to a church bell which drove away the Chaos forces every time it rang. The bell and the powers of the Warp also managed to keep the Sisters alive for over a century in this state of conflict.
During the early stages of the Indomitus Crusade Saint Celestine, Inquisitor Greyfax, Longinus, and Black Templars Marshal Godshelm traveled to San Leor in their efforts to protect Ecclesiarch Decius XXIII. They discovered the state of affairs on San Leor and rescued the embattled sisters and reclaimed San Leor.