So this is a vague concept right now. Something that I thought of a couple decades ago now:
To all appearances, a group of amateur demonologists/cultists have managed to some a demon. The demon is mostly humanoid with the stereotypical red-skin, horns and such but not really very grotesque or inhuman. Probably has the sexy-demon thing going on.
It seems this demon has taken over and is leading the cult into further evil.
In reality, however, instead of reaching into Hell or a similar supernatural realm, they’ve snatched a mortal from a timeline where sentients evolved slightly differently. Their summoning spell is imposing on the summoned individual the subconscious expectations they have of a demon while the victim is a passenger in their own body and a helpless observer as their body speaks alien words and does things that they thought physically impossible. For further matter they haven’t eaten, drunk or taken care of other necessities because the summonses don’t think demons need to eat, drink, sleep or answer nature.
If the summoner is defeated the “demon” would likely collapse into pained, sobbing lump in the ground in dire need of medical attention. This is especially true if the players have injured them.
Hm, interesting idea. You could even just say that the ritual grabs someone nearby and turns them into a demon – it doesn’t really need the alternate timeline backstory for the key part.
True. Hadn’t considered that.
Seems a very Unknown Armies kind of spell to me, which is cool – human will imposing itself on reality by consensual ritual instead of entities mucking about in our world.
Very Arthur C. Clarke “Childhood’s End” ideas…