From the Mitreo Fagan, Ostia, we know of his activity. He was a priest who achieved the highest grade of initiation.
The dedication of an excellent marble leontocephalic statue shows that he flourished at 190 A.C. In another of his inscriptions he professes himself Pater et Antistes Dei Iv(b)enis Inconrupti so(l)is invicti Mithra(e). Pater and priest of the God, the Uncorrupted Youth, the Unconquered Sun Mihtras. Here Incorruptus Juvenis provides a striking variation to the usual formula Deus Sol Invictus Mithras. I would seem that G. Valerius sought to honour his god with inscriptions that departed somewhat from the hackneyed formulas, for we also have a unique epithet on the third remaining monument erected by him, a sculpture of the turoctonic Mithras. The inscription reads: Sig indeprehensivilis dei, statue of the Unsurprisable God.
It would not be unreasonable to assume that this clergyman introduced into his inscriptions epithets familiar from the Latin Mithraic liturgy. Mithras as Indeprehensibilis, lit. 'he who cannot be caught off guard', is nicely paralleled in the Av. Yast to Mithra (It I0), for example verse 45 'Protecting in front, protecting behind, a watcher and scanner, undeceivable (adaoyamnō)... with fore-knowing mind, lord of ten thousand spies, omniscient, undeceivable', or verse 141, 'Victorious, equipped with a well fashioned weapon, watching in darkness, undeceivable; the strongest of the strongest, mightiest of the mighty, most insightful among the divinities; victorious, accompanied by Fortune; he who has a thousand ears, ten thousand eyes, the lord of ten thousand spies, omniscient, undeceivable.' Indeprehensibilis would correspond most closely to Av. adaoyamna- 'undeceivable', occurring six times as a standing epithet of Mithra.
—Mithraic Studies: Proceedings of the First International Congress of Mithraic Studies
, Volumen 1
Other brothers from Ostia
The marble Aion from the lost Mithraeum Fagan, Ostia, now presides the entrance to the Vatican Library.
C. Valeri/us Heracles pat(er) / et C(aii) Valerii / Vitalis et Nico/mes sacerdo/tes s(ua) p(e)c(unia) p(o)s(ue)r(unt). / D(e)d(icatum) idi(bus) aug(ustis) im(peratore) / Com(odo) / VI et / Septi/miano / co(n)s(ulibus)
Gaius Valerius Heracles, father, and Gaius Valerius Vitalis and Gaius Valerius Nicome(de)s, priests, laid at their own expense. (Statue) dedicated on the ides of August, under the consulates of Emperor Commodus for the sixth time and Septimianus
This white marble relief depicting a lion-headed figure from Ostia is now exposed at the Musei Vaticani.
C. Valerius Heracles pat[e]r e[t] an[tis]/tes dei iu[b]enis inconrupti So[l]is invicti Mithra[e / c]ryptam palati concessa[m] sibi a M. Aurelio / . . . De Rossi supplies: Commodo Antonino Aug(usto).
Gaius Valerius Heracles, father and priest of the unconquered sun god Mithras, young and incorruptible, made (?) the crypt of the palace, which was granted to him by Marcus Aurelius [---]
This monument bears an inscription that describes the god Mithra as young, which is quite unusual.
C(aius) Valerius Heracles pat[e]r e[t] an[tis]/tes dei iu[b]enis inconrupti So[l]is invicti Mithra[e / c]ryptam palati concessa[m] sibi a M(arco) Aurelio / ---
Caius Valerius Heracles, Father and servant (antistes) of the young (and) incorruptible god Sol invincible Mithras, has (arranged?) the crypt of the palace, which was granted to him by Marcus Aurelius [---]
The sculpture has an inscription where Mithras is called the undiscoverable deity.
SIG(num) INDEPREHENSIVILIS DEI C(aius) VALERIVS HERACLES SACERDOS S(ua) P(ecunia) P(osuit)
L(ucius) SEXTIVS KARVS ET
Lucius Sextius Karus and Gaius Valerius Heracles, priest, placed at their own expense the statue of the god indeprehensibilis.