Eight Ways to Make Your Games Really Scary for Halloween
1. Use Senses Other Than Sight - Things are really scary when it is hard to see. Make everything dark or dim so the characters have disadvantage on all perception checks and have to rely on other senses such as smell or hearing to figure out what is going on.
2. History - The past can be really creepy. Maybe someone died in a building. Maybe there is a body buried under the house. Past betrayal or crimes make things spooky and strange. You could also include ancestors of the characters and the horrible things they did. Have an old man in a tavern lit only by a fireplace tell the story of what happened long ago.
3. Use a Creepy Setting - A spooky forest with fog and creaking trees is pretty scary. A graveyard or a battlefield can create a sense of death and doom. A haunted mansion with rotting floorboards and lots of spiderwebs is creepy. Any place someone has died… any place someone came back from the dead… any place fiends have entered the material plane…
4. Undead - This goes without saying but undead are creepy and scary. Don't call them by their names. Instead, describe what they look like. Calling something a ghoul is not nearly as scary as saying, “It is a hunched-over beast with long claws and sharp teeth and sunken eyes. It appears humanoid but you can no longer tell what race it once was as its body is decayed and flesh is falling off in places. It smells like rotting death.”
5. Use Creepy Voices - Gentle whispers are a lot creepier than loud yelling voices. Practice making up creepy voices of copy ones from your favorite movie characters such as Gollum or the Nightsisters or the Oathbreakers Under the Mountain. Coughing and wheezing is extra creepy and gives you time to think of new things to say.
6. Blood - When you want something to be extra creepy, make it bloody. Blood isn't supposed to be outside our bodies so it is scary when it is. Use bloody handprints or footprints or pools of blood or even blood creatures of sentient blood. All of that is really creepy.
7. Mystery - When things are not explained, they are creepy. Create mysteries by making things up that don't really make sense. Why did the mirror not reflect the rogue? Why is the moon red? Why do we hear voices on the wind? Why is that dog following us? Why am I craving raw steak? Why am I sleepy after a long rest? If the characters don't know why something is happening, they will be scared.
8. Non-Combatant Ghosts - Spirits and ghosts that the characters see out of the corners of their eyes are scary. Maybe they can talk to one of the ghosts and get some creepy warnings about the darkness that is approaching or the way the characters will all die a horrible death. Ghosts can be suffering or filled with regrets from their living days. Ghosts might give away the characters position or give the characters bad advice. Or a ghost might even be friendly and helpful, but just having a conversation with someone who is dead would be really creepy.
Happy Halloween!!