Biography of Thrasyllus of Mendes
It has long been a mystery how and when the god Mithras was introduced to Rome. Mithras became very popular in the later Roman empire and many have speculated how this 'new religion' might have developed from the more ancient deity Mitra. A leading writer on the subject is Roger Beck who suspected that the astrologer Balbillus, the son of Thrasyllus, was a leading candidate as the person who effectively created the Roman mysteries of Mithras. Roger Beck elaborates on the idea that the new religion may have emanated from the Royal Court of Commagene (a kingdom which now falls in modern day Turkey / Syria). Franz Cumont had previously identified a link with the kingdom of Commagene. So it is interesting to note that Thrasyllus' wife, Aka, was a Princess from Commagene and may therefore be part of the link.
It has also been noted that Thrasyllus has been described as the most profound scholar of his age. It is recognised that he distorted Platonic doctrine and mixed it with Neo Pythagorean and Oriental occultism. In short, it is possible that Thrasyllus played a key role in creating and promoting the new mysteries of Mithras. It now seems possible that he introduced them to Rome when he accompanied Tiberius there from Rhodes in around AD. Tacitus records Tiberius's interest in astrology, 'the Chaldean Art', which he learnt from Thrasyllus when in Rhodes. Tacitus also records that Thrasyllus was one of Tiberius's closest companions.
—Graham Baker (2021) Ovid Decoded: The poet’s arch enemy unmasked and linked to the introduction of the cult of Mithras to Augustan Rome.