This thread is for compiling a list of things in The Way that are related to Christianity. This is what I can think of so far, but I feel like I am forgetting some things and other people can probably come up with more.
The Way was a term used for early Christianity.
Gaius has an attack called Trinity.
Slade has an attack called Outer Darkness.
Gharon has an attack called Longinus.
One of the transcendental auras is called Rapture.
Eyashu may be an anagram for Yeshua and Episode 5 has the hidden message, "Yeshua Save Me". (See this post.)
Johann Tetzel has been discussed a lot here.
I remember a discussion about the messages in the game over screen being related to Christianity:
"Where is your hope?"
"Death has lost it's sting."
"Help me. I'm afraid."