A dog-headed novice leaves his monastery at the command of the elder to capture and tame the remaining mythological beasts which threaten 4th century Jerusalem.

Yeah, it's a fantasy comedy along those lines. The maiden subplot is a love triangle with a twist. I don't want it to veer into spoof, because I lose any chance at true emotion.

A challenge to your logline is that the time setting is one very few people are likely to know anything about. On the other foot, the obscurity of the period gives you greater creative license to make whatever you want with the confusing history and multiplicity of legends.

Seems to me a better focus might be to do an origin story on St. George as the protagonist with Christopher as his sidekick/ally. (With St. George as the focus, you can better work in the "B" story of the rescue of the maiden.) Make it buddy/bromance film. In the style of a "Monty Python" send up of the period and people.

fwiw.

Having the head of a dog can be both a blessing and a curse. A dog-headed, etc. That should address the character flaw.