Many apologies: I clearly had David Lynch's "Homo Elephantinus" (& Mr Merrick!) in mind when I erroneously posted 'O Merrice'.

As you say, this should properly read:
"O Karras, perfide sus".

As for the title, I hate to be deflationary but a simple "Exorcistus" would probably suffice for this most elegant, intelligent and gripping motion picture....

In vomitu viridi
T.L.