Nightmare is a distorting negative dreamworld that is home to the sinister Nightmarens including its creator Wizeman the Wicked, and a location in the NiGHTS universe. This place within the Night Dimension is where Visitors (dreamers) go when having bad dreams.
NiGHTS reaches Nightmare when they take on a Nightmaren boss. Nightmare is reachable in the Dream Gate by falling in the strange dark ocean or being captured and taken by Wizeman into his dark kingdom. If a Visitor falls into the dark ocean and Wizeman himself manages to steal their Ideya, they will become doomed to be within Nightmare in their sleep forever.
Some stronger Nightmarens of higher ranks such as the ruthless Nightmaren jester Reala has a certain (yet somewhat limited) ability to shape the Nightmare realm to their own liking (such as the opera songstress Puffy with her fun-house arena or the ugly Bomamba with her huge black cauldron at the center of her massive castle-like chamber or the ferocious beast Girania with his gloomy coliseum) but they still have the unlimited power of interdimensional teleportation which they use to transport both victims and enemies alike there where there would be no escape.
NiGHTS, since defected from turned away
NiGHTS fought, defeated and soon vanquished Wizeman twice in NiGHTS Into Dreams and finally NiGHTS: Journey of Dreams with the help of certain good Visitors, so the evil kingdom of Nightmare would never expand and spread its darkness.
- Wizeman the Wicked - Creator of the Nightmare realm, well-known Level 1 Nightmaren, and lord of nightmares.
- Reala - A first level Nightmaren and loyal right-hand minion of Wizeman.
- NiGHTS - Former Nightmaren turned Nightopian and hero of the Night Dimension.
- Bomamba - An ugly feline witch and a Level 2 Nightmaren.
- Cerberus the Hellhound - A ferocious canine beast and a second level Nightmaren.
- Chamelan - A crafty chameleon magician and a Level 2 Nightmaren.
- Clawz - A fiendish feline creature and a second level Nightmaren.
- Donbalon - A laughing clown and a Level 2 Nightmaren.
- Gillwing - A monstrous tadpole-like dragon and a second level Nightmaren.
- Girania - A giant gladiator-themed piranha and a Level 2 Nightmaren.
- Gulpo - A giant hungry piranha and a second level Nightmaren.
- Jackle - A maniacal jester and a Level 2 Nightmaren.
- Puffy - A giant rabbit-like opera songstress and a second level Nightmaren.
- Queen Bella - A giant spider queen and a Level 2 Nightmaren.
- It is sometimes called the "Nightmare World".
- The world of Nightmare made an appearance as a vast warping DLC stage with Deadly Six Bonus Edition under the name "Nightmare Zone" in Sonic Lost World.