Around 1070 the energetic Bishop Burchard II of Halberstadt had Ilsenburg Abbey reformed by his nephew Herrand, whom he brought from Burchardi Abbey in Würzburg and appointed as Abbot of Ilsenburg in the 1060s. The intention was to reform the abbey in line with Cluniac thinking. Through donations Ilsenburg Abbey was already one of the richest Benedictine abbeys in Saxony during the 11th century.
The new spiritual thinking and faith had a distinct effect on architecture. Churches showing these new characteristics of reform are known as reform buildings with Hirsau motifs. These reform buildings (about 150) include not only Benedictine monasteries but also, for instance, buildings of the Augustinian canons (for example in Hamersleben). The second Romanesque abbey church in Ilsenburg was built between 1078 and 1087. It was the first German Benedictine church to have a triple nave at the east end and other reform characteristics, which were then taken over by the so-called Hirsau churches - i.e. before the famous abbey church of Ss Peter and Paul was built in Hirsau between 1082 and 1091.
Feldtkeller writes in 1937 about the relationship between Ss Peter and Paul and Ilsenburg Abbey: In Ilsenburg it can be seen in the spatial separation of the chorus minor and in the omission of a crypt, as well as in the triple nave of the choir, which ends in three apses in the north German style, as opposed to the south German style of Ss Peter & Paul in Hirsau (consecrated in 1091), which is rectangular.
Herrand remained at Ilsenburg until 1090, when he, in turn, became Bishop of Halberstadt. His energetic activity benefited not only the abbey. Repeated interventions and the Royal charters for Burchard’s church testify to his high standing at Court during 1063-1064. From 1068 he again enjoyed the goodwill of Heinrich IV. In 1071 he consecrated the cathedral at Halberstadt, newly rebuilt after a fire in 1060.
1074 saw a major assault by the Saxons on the Harzburg of Heinrich IV. The bodies of his son and of his brother Konrad, buried there, were saved and, it is thought, were reburied in Ilsenburg Abbey. But on 13th June 1075 near Hohenburg on the River Unstrut the King was victorious over the Saxons. Bishop Burchard, who had taken the side of the insurgents, was arrested and banished to Hungary. He was then involved in various battles. On 5th April 1088, during an uprising in Goslar, Bishop Burchard was seriously injured and died the next day at Ilsenburg. He was buried in the choir. According to an inventory of 14th April 1610 the abbey was still storing “1 large red velvet drape to cover the founder’s tomb” in a big locked pinewood chest in a vault.
The aim of the Ilsenburg reform movement was already in the 11th century to create a circle of monasteries within the Benedictine Order, which would be legally dependent on one abbey. For the monasteries of the Herrand reform constitutional models were developed to which Bishop Reinhard referred at the beginning of the 12th century, when he reformed monasteries and convents but did not bring them within the Ilsenburg group. This association was actually made up of the monasteries of Ilsenburg, Wanlefsrode, Huysburg, Wimmelburg, Hillersleben, Harsefeld, and St. Maria / St. Ägidien in Braunschweig, of which only Wanlefsrode was legally dependent on Ilsenburg.