During the Saxon Wars, the stronghold was repeatedly occupied by Widukind, leader of the resisting Saxons (those refusing to adopt Christianity and the overlordship of the Franks), and then abandoned to Charlemagne's forces as the Saxons retreated to the home of Widukind's in-laws, today Denmark. Local lore states that as Charlemagne's forces approached, the town's common folk would move into the Drachenholler, a vast system of underground gypsumcaves beneath Eresburg, where they remained unnoticed until Charlemagne's people left. Though only a legend, the caves can still be seen, along with several watchtowers dated to the same time period (circa AD 800).
Very near Eresburg is Priesterberg, a hill overlooking the valley of the Diemel. This was reportedly the location of Pagansacrificialrites in the pre-Christian era. It is also thought to be the home of Irminsul, a sacred tree or pillar which represented the Germanic central pillar of the world. In AD 772, Charlemagne destroyed the Irminsul on Priesterberg (elsewhere reported as "near Paderborn" or "near Eresburg"). The Irminsul was replaced by a stone structure, possibly a tower, the crumbling remains of which can still be seen.
Around AD 800 the first Christian church was constructed in Eresburg proper. Although the current church in Obermarsberg only dates to the 13th century, it is at least the second or third church to be built over the remains of Charlemagne's original church.
