[quote=kapuchu]
I'll have to copy Monochromatic here: Not to rain on your parade, Eldritch, but the Nightmares don't have invisibility spells :/ They're shadows, so to speak, and can hide in them simply because they look like a shadow themselves. That coupled with their ability to travel through solid objects gives them an illusion of being able to turn invisible. Also... A blood sacrifice for those thingies... Am I right to assume that said blood is coursing through them, then?
[/quote]

Thats twice someone has said that to me in so many hours, anyhoo, I'll sort it out, I am just repeatedly uncertain of the established rules given I am relying on sparse details from original canon and the mod's headcanons.

The blood sacrifice part? basically it can either use its own or go and kill something and coat the runes in it, it only needs to be done relatively infrequently however, but its the price they pay for the spell.