Which peoples inhabited this territory where Saint Walpurga was an abbess in the 8th century?
the Franks
Title: Walpurgis Night
Passage: Walpurgis Night is the English translation of Walpurgisnacht ] , one of the Dutch and German names for the night of 30 April, so called because it is the eve of the feast day of Saint Walpurga, an 8th-century abbess in Francia.  In Germanic folklore, Walpurgisnacht, also called "Hexennacht " (Dutch: "heksennacht" ), literally "Witches' Night", is believed to be the night of a witches' meeting on the Brocken, the highest peak in the Harz Mountains, a range of wooded hills in central Germany between the rivers Weser and Elbe.  The first known written occurrence of the English translation "Walpurgis Night" is from the 19th century.  Local variants of Walpurgis Night are observed throughout Europe in the Netherlands, Germany, the Czech Republic, Slovenia, Sweden, Lithuania, Latvia, Finland, and Estonia.  In Denmark, the tradition with bonfires to fence off the witches going to the Brocken is observed as Saint John's Eve—essentially a midsummer celebration "with witches".
Title: Francia
Passage: Francia or Frankia, also called the Kingdom of the Franks (Latin: "Regnum Francorum" ), Frankish Kingdom, Frankish Empire, Frankish Realm or occasionally Frankland, was the territory inhabited and ruled by the Franks, a confederation of West Germanic tribes, during late antiquity and the Early Middle Ages.
Title: Altmünster (Mainz)
Passage: The Altmünster abbey near Mainz, Germany, was reputedly founded by Saint Bilihildis (d. 734), who served as the first abbess; however, it may well be a 7th-century foundation.  Though founded as a Benedictine abbey, it adopted the rule of the Cistercians in t he 13th century.  It was dissolved during the secularization of the 18th century, and the abbey buildings were demolished.  The abbey church was given to a Protestant congregation in the early 19th century; it was destroyed during World War II but rebuilt and reconsecrated.
Walpurgis Night Francia