Cannot Dream

"The Nameless One: I... don't have dreams, actually

Kesai-Serris: Truly? How sad! Even fiends and devas dream, you know. Are you certain you don't?

The Nameless One: Quite certain. No dreams, at all."

- Planescape Torment

Exactly What It Says On the Tin.

For whatever reason, a character cannot dream. Perhaps they are dead already, or has spent too long in cryo-sleep, but their ability to dream is gone. This tends to indicate that something is inhuman or 'off' about them.

May also be caused by a Dream Stealer.

In Real Life this would be extremely dangerous, dreaming being necessary for mental health and memory. Most people who "don't dream" in fact dream very deeply and therefore have more difficulty than most in remembering their dreams.

Anime & Manga

 * Rei in Neon Genesis Evangelion.
 * In Jing King of Bandits, Campari lost his ability to dream. He subsequently gained the ability to steal dreams from other people.
 * Kanami in Darker Than Black told her colleague that a Doll who moved "sees a dream". Then she had to clarify that she joked and Dolls don't. Since they got some sort of encephalography equipment on their heads, we can assume that it's the certain knowledge at least as far as catatonics in lifesupport tanks are concerned. Contractors were said to never dream either, but with them and free-willed Dolls, it may be smoke and mirrors again.

Comic Books

 * In The Sandman, people lost their ability to dream during Dream's imprisonment.
 * Villain Dr. Destiny in The DCU lost his ability to sleep and thus dream. He later appeared in The Sandman.
 * Bionicle has the Dreaming Plague that wiped out most of the Iron Tribe, caused by Annona.

Film

 * In Inception, one side effect of using the PASIV is that you eventually lose the ability to dream normally.
 * Krank in The City of Lost Children is unable to dream. He's kidnapping children and stealing their dreams, which sets off the plot.
 * In Die Another Day, the villain Gustav Graves was said to be unable to dream.
 * Specifically, he is unable to enter REM sleep, a Real Life condition. He has to use a machine to do it for him, or he'll start suffering from severe psychosis.
 * The immortal Eternals of Zardoz cannot sleep or dream, since sleep was strongly related to death.
 * The Villain Protagonist of The Young Poisoner's Handbook. This becomes important when The Shrink in the prison wants him to talk about his dreams, so he "steals" the dreams of his cellmate.
 * Terri from Hellraiser III Hell On Earth.

Literature

 * Vampires in most incarnations (already dead).
 * Brutha in Small Gods has never had dreams, which may be related to his Photographic Memory somehow.
 * In The Voyage of the Dawn Treader, a man who went mad at The Isle Where Dreams Come True is afraid to sleep because he doesn't want to dream; at the Island of the Star there's food which makes one go to sleep without dreaming. He's thrilled.
 * In The Exile of Borghild Brynlaging, Scyld (and Borghild, but she is not aware of it as she no longer even remembers dreaming). The reason is that they're dead and have no separate spirit forms that can leave them in their sleep.
 * A character in a Celtic fairy tale (reprinted in Traditional Tales From Long, Long Ago by Philip Wilson) is unable to dream but is otherwise perfectly normal. His employer suggests a way to guarantee he'll have dreams: make his bed in the fireplace. He ends up with a thoroughly bizarre dream that ends when his wife wakes him up and he's halfway up the flue.

Live Action TV

 * Kai, last of the Brunnen-G (dead) on Lexx.
 * Most of the Enterprise-D crew temporarily lost their ability to dream in the episode "Night Terrors".
 * Alonso from Earth Two spent decades in "cold sleep".
 * There was a Villain of the Week in Supernatural who couldn't dream, and killed people in their dreams out of jealousy.
 * Jaffas of the Stargate Verse do not dream, as they do not technically sleep, only entering a deep meditative state.

Tabletop Games

 * In Eberron, Kalashtar have lost the ability to dream. That's because they are inhabited by exiles from the realm of dreams, and if they return, they will be destroyed by that realm's despotic lords.
 * The undead of In Nomine have also lost the power to dream, along with many other simple human pleasures. Technically, they don't even need to sleep, but if they do, they can no longer reach the Dream World of the Marches without supernatural help -- they've actually severed themselves from humanity's collective imagination.

Video Games

 * In Dragon Age, mages who have been made Tranquil are severed from the Fade, which prevents them from using magic or being possessed by Fade demons but also robs them of their ability to dream, not to mention their ability to feel emotion.
 * Dreaming in Dragon Age essentially means slipping into the Fade when you're asleep, where spirits construct dreams for you. This is somehow tied to the ability to use magic. Dwarves can't use magic, can't slip into the Fade, and by extension can't dream.
 * Kirby's Adventure starts off with the residents of Dream Land losing the ability to dream because King Dedede stole the Star Rod, which grants them dreams. It's later revealed that he did this to stop a Nightmare from corrupting the Fountain of Dreams.
 * The Nameless One of Planescape Torment. The above quoted conversation is with a woman who talks about dreams. Her surprise indicates TNO's condition is very extra-ordinary, as she is in Sigl, where natives have a "seen it all" attitude due to the cities stats as a planar cross-roads. It's a bit of an oddity when the Kalashtar (see up) are latter introduced as part of the same "verse".
 * Arcueid is revealed in Kagetsu Tohya as being unable to dream when she complains of a nightmare. Her brain is basically completely turned off when she sleeps. Occasionally, even in this state she recalls things about her past, but says this can't be considered dreaming.
 * Averted with vampires in The Elder Scrolls. When infected with porphyric hemophilia (the disease that causes vampirism), characters begin to have horrific nightmares. The third nightmare ends with their full transformation into vampires. In some of the games, they continue to have nightmares after transformation as well.

Webcomics

 * In a variation, characters in Homestuck whose dream selves are dead are forced into contact with the Horrorterrors instead of actually dreaming when they fall asleep.
 * Most sufficiently advanced incubi and succubi in DMFA can't dream; instead, they experience dreaming by "surfing" the dreams of others. Also, they don't need to sleep, but if they do, they can easily sleep for days or even decades without noticing the passage of time.
 * In The Dreamland Chronicles, Dan in completely unable to dream.
 * Alex himself was dreamless for years between the time the sword he just found was confiscated and the time he got it back.
 * Pibgorn Why am I dreaming? I haven't dreamt in a thousand years!

Western Animation

 * In the animated series adaptation of The Neverending Story, one episode states that bag guys don't dream, along with some other creatures.
 * In Titan AE, Preed states that Akrennians do not dream. Of course, they are a totally different species...