Hmm.......horror game? I could help you.
1. Find some very scary sound (like the ReDead from Ocarina of Time)
2. Find Pictures (Creepy monster, Zombies, ect.)
First, make a scary-looking place, then when you enter it or outside, change the Screen Tone to like 50% (on each).
Next make an event, make it Parrarel Process (inside the scary-looking place), there add the sounds you found. Put the command wait after that.
Next, on the same event (if you want), add Lightning effects, to do that you could:
a. Add very loud sound of thunders
b. Flash the screen white for 0.2 sec.
c. both
Well thats the basic so later ill post the actual command for it (Just tired today)
Also, how can you take a screenshot? Like some do? so it would be easier and show you how it will work on the game.