Some believe that Externsteine was a center for Saxon pagan rituals. Like many other European pagans, Saxons were known to gather in nature to worship their gods. Just as the Celts, Balts, and Slavs kept sacred groves, so, too, did the Saxons. The towering monoliths would have provided a sense of awe and an allure of the supernatural. It seems a natural place for any Earth-centered religious group to worship.

It is said that when Charlemagne forcibly converted the Saxons to Christianity, that he destroyed pagan temples and banned the use of sacred sites such as Externsteine for such practices. However, we are again left with little evidence to confirm this story. Based on what we know of pre-Christian Saxon worship, and of Charlemagne's conversion campaigns, the theory is plausible, but the evidence simply cannot substantiate the theory.

We do know that there were Saxons in the region where Externsteine is located. We also know that Charlemagne reportedly destroyed many Saxon pagan religious sites such as sacred trees, groves, temples, and pillars known as Irminsuls. An Irminsul was a tall wooden post erected in areas of worship. Scholars can only speculate on their meaning, but many think that it may have a connection to Yggdrasil, the Norse World Tree, or that it may have had a connection to a lower god called Irmin. It is also speculated that Irmin was a "kenning" (or nickname) for another major deity such as Frey or Odin.