This chapter is describing an actual event where the Armenian king Tiridates performed a Mithraic ceremony as an oath of loyalty to Nero. However, the imagery used is actually that of Mithras, the Roman version of the god that only gained this form later in the 2nd century. Most likely Tiridates would have used the original solar-crowned upright Mithra imagery instead. Also, it's a bit ass-backwards. While Mithras cult was already extant in the Roman Empire, it was Tiridates' obeisance to Nero that started Mithras' popularity as a god of vows and oaths in the Roman army and eventually birthed the Mithras figure depicted here. In Armenia itself, by this time Mithra had evolved into Mihr and was about to be replaced by the new religion of Christianity.