Oh crap, we got ghosts and shit running around too? I haven’t seen any yet, but one time I was in a lab barracks armory and got randomly gooed by what the game called ectoplasm. I couldn’t find a source of it, the logs didn’t say anything about any enemies, and it didn’t happen again. I thought it was a bug of some sort. I think I may have been wrong…
Do you need IR goggles or something to see them?
I always wear a relic and a holy symbol just in case they do something; maybe they will force them to avoid you or prevent curse effects? As for killing it, electric weapons might work. Fire is always a good choice as well. Even if you can’t kill the damn thing directly, destroying its hiding place via fire or explosives might force it out into the light, which may kill it.
My current character is extremely well equipped, if I run across one I’ll inflict science on it until I figure out a few ways to destroy them, and what does/doesn’t affect them, and post it.