I'm running out of time for this game jam but I've got enough features in place now that I've started constructing a playable level. New features include a cool effect when changing between worlds, sound effects, tweaked controls and collisions, highlighting objects that only exist in one world by rendering them with a special shader in the other world, and a light-based stealth system with lights that can also exist in both worlds or just one.
Thanks! My current plan is actually along the lines of the player being quite fragile - the AI will be equipped with crucifixes, holy water, stakes, etc. and if you get close to them with them aware of your presence they'll charge at and attack you (one-hit kill), forcing you to rely on stealth. At the very end of the video you can see I dropped down in the reflected world because there was no light on that side, allowing me to get right up to the target before switching back to feed / win the level.