The south transept is of great importance in the history of the convent and the church. Up to 1824 the Thiatildis chapel was separated from the nave and the aisle by a wall.
Originally the tombstone of the first abbess of the convent, Thiatildis, the niece of the founders of the convent, Everword and Geva, was in the semi-circulat apse on the north side. Thiatildis, who had always been venerated as a saint in Freckenhorst, was endowed with the „honours of the altars“ by Bishop Bernhard von Galen in 1669. He donated an exceptionally artistic silver shrine for her mortal remains, which is enclosed by modern bronze latticework on a basalt base, and stands on the original burial place.
Ten corinthian columns support the hipped roof of the highly-decorated shrine, created by Heinrich Ernst from Düsseldorf. At the front end is a dedication and the coat of arms of the bishop, the donor. The reliefs of St Ann, St Katherine, St Walburga and St Elisabeth represent Thiatildis’s character: motherliness, scholarship, medical knowledge and compassion.