- The Ravenloft campaign setting is a textbook definition of Ironic Hell.
- The Nightmare Lands boxed set is quite a nightmare fuel filled read in itself. Imagine you are a doctor who has made breathtaking advances in medical science related to insanity. Imagine you come across a pattern of similar nightmares in a string of patients. Imagine you realize the patients aren't psychotic, they really are being tormented by nightmarish incomprehensible beings that worm their way into your nightmares. Imagine when those beings notice you noticing them. Imagine there's no escape from them because the Nightmare Lands are a Domain controlled by these beings, who are collectively its Dark Lord, and that the Lands conjoin the Deep Ethereal, where all humans go when they sleep. Welcome to Dr. Illhousen's very sleepless and fun life.
- The Wishing Imp is a magical statue-slash-Jackass Genie that follows you around and twists your wishes. And eats your soul if you don't make any— or if you do.
- Illithids note are scary enough. One of the Darklords of the place is an Illithid elder-brain. The stuff that torments it? Illithid Vampires.
- Darkon is a very subtle kind of Nightmare Fuel. The place eats your memories and replaces them with memories of you having lived your life there your entire life. Which means that anyone there cannot, almost by definition, trust their own memory...
- Oh, and those memories you've lost? You can't access them, but Darkon's darklord can. Because they're in his library, filed away in a book with your name on it that wrote itself. All your secrets, your plans, your loved ones, are in there. And you no longer remember to dread or fight back against whatever harm he might do with that knowledge.
- The Bleak House. Every room in the place is designed to unsettle the characters (and players) from a room made in shadowless monochrome with a permanent echoing spell to torches that give off monstrous shadowy. Every patient, orderly (and the characters) are made to dress in Grey robes, with ugly masks they can't take off, so you can't tell friend from foe, can't even recognize yourself. The kicker? Every night, when the characters are asleep, they're subjected to several different types of "Psychological Experiments" ranging from inducing new Phobias to purposely inducing Split Personalities and two words: Psychic Amputation. Not to mention the Warden has a nasty habit of letting you think you're getting away with a clever escape plan, before he swoops in at the very last second, and did I mention the Orderlies are dressed exactly like the patients and they're a type of vampire that drinks cerebral fluid.
- One adventure features a trapped coffin that if some unfortunate victim gets stuck in it, but manages to escape before ten rounds, that they start acting and suffering the effects of vampirism for the next several days (but not actually turning into one). Which leads to the idea that the poor victim might end up 'being staked for the better of sapient-being-kind' before his friends realize the ruse. Or worse, imagine being the Paladin or Cleric (or a Ranger with special enemy Undead) - imagine their horror.
- In the greater D&D cosmology, gods restrict themselves to their own domains, e.g. the gods of Toril have no influence on Krynn. Ergo, clerics from the Forgotten Realms have to find a new god if they end up in Dragonlance (which, philosophically, is a lot harder on a person than erasing "Mystara" and writing "Majere" in its place on your character sheet). That is not true for Ravenloft; while no true gods have power in Ravenloft (late 2E Vecna notwithstanding), which has its own pantheon of ill-defined deities, outsider clerics still have power. Something is answering those clerics' prayers. It's heavily implied to be the Dark Powers, though WHY is anyone's guess.
- Jacqueline Montarri's "private storeroom". A deep, long, dark basement... filled with the undead heads of all the women she's murdered so that she can wear them for herself. Each head is still possessed of its full sentience, but incapable of doing anything on its own, and when she wears it, its consciousness is suppressed. They don't age, except when Jacqueline herself is wearing them, and the write-ups are extremely vague on whether or not a head will be destroyed if she wears it for too long, or if they just keep aging into a hideous crone's face. They can't die by any method they know. So they just sit there. In the dark. Weeping, screaming, sobbing and babbling as they descend into madness from the sheer horror of their existence. There's hundreds of them down there. And their numbers just keep growing, because Montarri is constantly after new faces to wear. No wonder it's treated as a high-ranking Sinkhole of Evil in the 3rd edition!
- The Death's Head Tree is basically a fucking zombie tree. It's a tree which has the rotting, screaming, biting humanoid heads of its past victims as "fruit". The tree often attempts to lure people in close by getting the heads to softly call out for help, and then spitting seeds into the bodies of those who get too close (out of curiousity or an urge to destroy the tree), which then begin to spread through the person's body. Sometimes the heads fall off and then they float around looking for victims, some of whom they'll chase for miles. On the positive side, the wood of the tree is magical enough to be crafted into high quality magic items.
- The House of Lament is haunted by a train-raped and murdered young woman just looking for friends, by killing those who step inside and trapping their spirits. The PCs can't get out through any means mundane or magical, and the hauntings get progressively more intense and frightening the longer the PCs stay inside, playing as much on personal fears. The worst part: the only way the doors will open to let them out is that somebody HAS to die.
- Marilee Markuza the child-vampire exists to play on adult fear. A common tactic for her is to act as a lost or hurt child to lure in people only trying to help.
Nightmare Fuel / Ravenloft