This thesis on the Valentinian gnostic Mark the Magician presents a survey of Mark’s doctrine and a portrayal of the cult and the life in the community of the Markosians. In spite of the considerable number and quality of sources Mark and his adherents have been neglected in modern research. But Irenaeus’ and Hippolytus’ reports on this Valentinian group are very valuable since they allow us to look at the form and the sequence of the rites in the gnostic service and at the mixture of different religious and non-religious traditions that shaped Mark’s teachings. Mark adapted a manifold body of thoughts and traditions in a process of transformation and merged them together in a kind of associate network. The essence of this synthesis of ideas was deeply syncretistic.