Attis (Ancient Greek: Ἄττις or Ἄττης) was the consort of Cybele in Phrygian and Greek mythology. His priests were eunuchs, the Galli, as explained by origin myths pertaining to Attis and castration.
This ancient god apparently didn't make its way to the Roman consciousness until the time of Augustus. Its savagery seized the imagination of Catullus in his #63:
. . . So when she (no longer he) sensed that her manhood was gone,
while still staining the soil of the earth with fresh drops of blood,
she impetuously took up in her snowy-white hands your light tambourine,
Cybele, took up your mysteries, O Mother.
Shaking the hollow ox-hide of the tambourine with delicate fingers,
tremulously she began to sing this exhortation. . .