Born in central Spain, Casilda was the daughter of the emir of Toledo. Though a Muslim, she had a reputation for being kind to Christian prisoners. After she became sick, she went on a pilgrimage to the shrine of San Vicenzo de Briviesca, which was famous for its healing waters. She was cured and became a Christian, embarking on a life of solitude and penance in a cell near the shrine. Her name eventually was added to the shrine’s name, and she reputedly lived to the age of 100. In 1750 her remains were transferred to a new shrine.