In the medieval period, the abbess exercised the functions of a bishop, except for the sacramental ones, and those of a ruler, over the very extensive estates of the abbey, and had no clerical superior except the pope.

[1] It was founded about 845 by the Saxon Altfrid (died 874), later Bishop of Hildesheim and saint, near a royal estate called Astnidhi, which later gave its name to the religious house and the town.

Apart from the abbess, the canonesses did not take vows of perpetual celibacy; they lived in some comfort in their houses, with their own staff, and wore secular clothing except when performing clerical roles such as singing the Divine Office.

[3] She acquired from Koblenz the relics of (Florinus of Remüs) for the abbey,[4] and donated the processional Cross of Otto and Mathilde.

In the north of the territory was located the abbey's monastery of Stoppenberg, founded in 1073; to the south was the collegiate foundation of Rellinghausen.

Approximately 3,000 farms in the area owed dues to the abbey, in Vest Recklinghausen, on the Hellweg and around Breisig and Godesberg.