Create a bio-mechanical cybernetic humanoid and then test out a world's worth of incantations and invocations to prove once and for all that 'raising the devil' was a load of nonsense.
The idea - if it happened to work - was to trap a demon or even the devil himself within the cybernetic creation and then control the entity from the outside.
They saw it as possession of an automated robotic humanoid, not a real human, and so the idea was passed through to the experimentation stage. Ideas rarely proceed how you want them to.
A short horror story with elements of a short science fiction story - 5000 words long - perfect for a quick read on the way to work or just as you turn in for the night!