Mithraism

It has left many monuments of itself here in Britain. At Rome the worship was extremely popular, and it may almost be said to have been a matter of chance whether Mithraism should overwhelm Christianity, or whether the younger religion by adopting many of the rites of the older one should establish itself (as it did) in the face of the latter.

Source: wiktionary

"Confirmation is mithraism. So is baptism, only it was blood instead of water. As to the sacrificial meal..." Mason put his fingers in his ears.

Source: wiktionary