The Roman army is undoubtedly the socio-professional milieu most affected by the cult of Mithras in the province of Pannonia. With a few exceptions, the Mithras cultores
were military of the Adiutrix Legion II, stationed in Aquincum. It can be seen that these Mithras-worshipping soldiers are found at all levels of the military hierarchy. The most important of these worshippers is certainly the legate of the legion, Gaius Tulius Castinus:
Deo inuicto/ Mithrae C(aius)/ lul(ius) Cast/inus leg(atus) Aug (usti)/ pr(o) pr(aetore).
'To the unconquered god Mithra, Gaius Iulius Castinus, legate of Augustus the procurator [made this offering].'
The legate of a legion, a member of the senatorial order, led the entire legion: he was therefore a person of primary importance. Tulius Castinus was also the governor of the province: in provinces with only one legion, the governor also led the legion located in the territory under his authority.
Gaius Iulius Castinus was in office in Inferior Pannonia from 209 to 212, which makes it possible to date the inscription fairly precisely. The career of this legate is also fairly well known. Before becoming legate of Inferior Pannonia, he was also legate of the legion I Minervia (205-208). He seems to have enjoyed the favour of the emperor Caracalla afterwards.
This inscription indicates that he was in Lower Pannonia at the beginning of the reign of Elagabal, which makes it possible to date the inscription to the beginning of the 3rd century.
—Olivier Latteur. La Diffusion du culte de Mithra dans les province danubiennes
Other brothers from Aquincum
This altar to Mithras is dedicated by a certain Gaius Iulius Castinus, legate prefect of the emperors.
Deo Invicto / Mitrae C(aius) / Iul(ius) Casti/nus leg(atus) Augg(ustorum) / pr(o) pr(aetore).
To the invincible god Mitra, Caius Iulius Castinus, legate prefect of the emperors.