Quote Originally Posted by MrUberGr View Post
There's a competition in one of the game shops in my city for a single session adventure. Over my time here, I've read many threads, yet two specific ideas have stuck in my mind. Unfortunatelly, there's not a single chance I'll remember when or where I found them, so I can't give credits to the original thinker.

I haven't thought the whole thing up. In fact, I'm just starting to put my thoughts in a line.

Basically the party gets sent to a place where many people have been dissappearing, to investigate. It could be a village, a trading post, a small island, whatever. The whole scenario is that two young twin girls that were murdered, rose as vengeful ghosts and are now unleashing their rage in whoever is unlucky and happens on their territory. I've thought of the setting to be something like a misty forrest, where time and space aren't exactly normal, I.E. teleporting traps, illusion walls etc. After fighting some appropriate monsters (displacer beast, will-o-whisp) they will finally get to the girls' lair. Be it a house, a cove or something else. And here is the most interesting point. As soon as they walk in to the lair, they'll be overcome by some illusion magic, and fall into a pit-trap two by two. Now, if you fall down, and see a goblin waiting for you, you'll mostly attack it. The plot-twist is that the goblin is, in fact, another ally. My issue here is how they players can actually overcome the mind trick and figure it out, before one kills the other. I haven't been able to devise a way.

My next issue is the final boss, the twins. I'd like to homebrew something were the one would be more of a fighter, while the other would be a caster. Some support mechanic, so the fighter would reduce the damage on the caster, and the caster would buff the fighter, just by being close to each other. No concentration spells etc. I will work on this over the weekend, since I do not have enough time atm, and post something less vague.

Any general ideas as to the setting, plot twists, some NPC(?) etc are all welcome! The most limiting thing is that it must be a single session (approx. 8 hours) long, meaning that it won't be the most easy thing to build up intrigue and tension. (I think)
It depends on what you're considering horror. Take a look at Extra Credit's YouTube channel for some good ideas on how to conduct horror games. Here, however, is the short version. The horror genre is essentially based on feeling powerless against an antagonist and building suspense on that. In RPG terms this means breaking most of the rules. Split the party, create encounters that cannot be won, kill characters intentionally. It also means lots and lots and lots of blind checks and saves.