The Campaign Builder's Guild

One thing I have been trying to bring into my campaign is the sense that evil outsiders are genuinely horrifying--not just more scary monsters but that just being in their presence is a violating experience. Has anyone else experimented with this, or does anyone else have ideas about how to do this?

Elements that work in film or stories for instance that are sometimes lacking in presentation in games include:
1. unnatural knowledge
2. uncanny movement
3. affecting the environment (lowering or raising the temperature, attracting vermin, etc)
4. posession
5. distortion of time
6. strong attraction effect upon the weak of mind

I believe it all boils down to the description. "Standard" demon and devil forms are typically humanoid, but I don't adhere to that whatsoever.

For instance, the one and only time a demon/devil has ever been run in my game was at the conclusion of a three-year campaign. It was called the "Dark Occupant", for lack of a better term. It slinked around upon spider-like legs that bent backwards (think the sort of jerky movement of the little girl in The Ring), was covered in molten flesh and its voice sounded like the continual shattering of windowpanes. It's eyes were as large as hurling balls, wet and seeping pus which crusted around the creases of an unnaturally wide smile filled with hundreds of teeth (like a gar has). The thing's hair was nothing more than a shock of smoke and shadow, and gave off the smell of burning sulfur (like the bitter smell of matches snuffed out).

Being around it induced miasma and sickness, similar to the sickness induces by ghasts. Of course, this was only heightened by conditional saves where one person would become sick, everyone else would become sick, etc... It also spoke sentences backwards (which, by the way was tremendously difficult for me to do - it took a lot of practice).

Many of the traits you described can be easily portrayed in game without so much as a short note by the DM: "You notice as you proceed down the hallway, the lights seem to dim and what looks like tiny spiders sneak in single file along the ceiling..." or such.

If you're looking for game mechanics, there are three or four sources that may give you what you need: the Book of Vile Darkness/Libris Mortis (if I'm not mistaken, both have possession rules), Heroes of Horror (rules for Dread, Fear, and Taint), and Unearthed Arcana (rules for some previously listed effects, and for Insanity). These mechanics could be applied specifically to demons and devils for the effect you want, though Dread and Fear aren't exactly the most well-designed systems and it's kind of hard to press specific emotions on characters in a game. Insanity (one of my favorite mechanics) works well for having a lasting, damaging effect on the players, as does Taint, but you will have to decide if you just want it to function between humanoids and fiends or encompass a wider group (possibly including aberrations and such). Unearthed Arcana is part of the SRD, so you can probably just hop on over to the SRD page and check that stuff out.

I do agree with Moniker that a lot of it actually comes in the presentation. Holding off direct encounters can be great - maybe a creature with such sickness effects as the one he mentioned could lurk around for a while, leaving a few signs of their presence for the PCs to find and showing the PCs or people around them actively get affected, all the while not  letting the players see, hear, or even really know where the thing is.

I think (along the lines with Troll), anything that just leaps out at the players for a fight will be perceived just as an extradimensional monster to be fought.

It's one of the reason I put so much effort into my conception of "cosmic beings," and indeed, why I call them that. I think something more-or-less formless is going to be scarier than a monster, no matter how horrific its form. It's why possession works so well.

To your average D&D character (and player), any big scarier monster, even with a unique description, is just another big scarier monster. But the malevolent entity they cannot see or even fight, now that's scary (if done right, or just irritating if done poorly).

All of the 6 items you mention work well for creepy mood.

Further, along the lines of possession, consider people that are just slightly off. Something that's normal, only not quite, is scarier than something completely alien, maybe because we (the players) can actually project ourselves more fully into something closer to reality. For example, the creepy little girl motif, the guy with (sometimes) black eyes and a too-knowing look, or the old hag that always seems to be in the right place at the right time, until you try to corner her and she's gone.

Taint really helps, as well as mood and description. If you want your players to take the game seriously, you regrettably do need to limit the joking and shenanigans that go on at the table.

But I think taint is a really good mechanical way of making people afraid. Also, call for will saves vs. fear, or fort saves vs. sickened/nauseated when these outsiders are encountered. Don't skimp on the details in the evils they do.

Atmosphere, in gaming, must be planned and set up.  Moniker's goes above and beyond and gets a GM purple dodecahedron.
Troll's comment is also on the mark.  If the first time the players experience the atmospheric changes is when the encounter stats, then the effect is limited.  

Taking this a step further, I generally have been keeping the lights turned up and have even found some cheerful in-town music to play when the guys are in Igbar or Miston (in-town), and have my NPC's speak very loudly.  But light candles, dim the overheads, turn on Midnight Syndicate, and speak in a lower tone when the players move back into the Sheering Tomb or Wizern's Underthrone.


And as has been said before, telling the PC's that their lanterns are sputtering crazily, that there is a flowers-over-rotting-meat pungency in the air that is requiring them to make a fortitude save, that the shadows on the wall from the lantern's light seem to be closing in on them and their is a cold, rankness pervading that makes thier old wounds hurt...all BEFORE the encounter with an Unbound Entropic...before is the key.

I like your little list, Tybalt.  Possession is something I barely use...
I'm sure the above comments are old-hat to most, but reminders are never bad.

I agree with Pheonix in that it's the small things that make the difference. Stuff that's just slightly off seems to spook my players more than stuff that's downright freakish.

For instance, one of my sessions I played them all slowly going insane. Just shifting the descriptions as they passed through rooms, re-arranging them, and toying with 'visions' ('You see an orc' "I attack the orc" 'what orc?') worked well also.