Darkrai

Darkrai is a Legendary Pokémon introduced in the Generation IV games Pokémon Diamond and Pearl Versions. It is a -type Pokémon with the ability to put others to sleep and give them never-ending nightmares, although Darkrai does this as a defense mechanism rather than out of malice. In a majority of the core series titles, Darkrai is featured as an Event Pokémon. In some of the spinoff titles, a Darkrai is featured as a major antagonist.

In the core series, Darkrai is genderless, but is often regarded as male in spinoff titles because his archenemy, Cresselia, is female.

Pokémon Diamond and Pearl Versions / Pokémon Platinum Version
In Pokémon Diamond and Pearl Versions and Pokémon Platinum Version, there is only one Darkrai, and it can be found on Newmoon Island, which only becomes accessible if the player character has a Member Card, distributed exclusively via real-world events.

Pokémon Legends: Arceus
In the post-game of Pokémon Legends: Arceus, Darkrai can be encountered during the request "The Darksome Nightmare," where it ambushes the player character at night in the Clamberclaw Cliffs area of the Coronet Highlands. The request can only be obtainable if the player has a savefile of either Pokémon Brilliant Diamond or Pokémon Shining Pearl on their Nintendo Switch.

Pokémon Mystery Dungeon: Explorers of Time and Explorers of Darkness / Pokémon Mystery Dungeon: Explorers of Sky
In Pokémon Mystery Dungeon: Explorers of Time and Explorers of Darkness and its associated title Pokémon Mystery Dungeon: Explorers of Sky, Darkrai is the main antagonist. He is the Pokémon responsible for the initial destruction of Temporal Tower, halting the flow of time and driving Dialga to insanity.

When Grovyle, Celebi and the Player planned to go back in time via Celebi's Passage of Time and prevent the collapse of Temporal Tower, thereby preventing Darkrai's dark world from existing, Darkrai intervened, attacking Grovyle and the Player as they traveled through time, separating the two. The Player is transformed into a Pokémon, and gets amnesia. Darkrai is not seen until later on in the game.

After defeating Regigigas in the Aegis Cave, the Player begins to dream about Cresselia, who tells them that their continued existence is causing a rift the fabric of space and time, as they originated from a non-existent future. Later, the Player and their Partner are alerted to the fact that Azurill has fallen into a nightmare that he cannot awaken from. With the help of Drowzee, the pair are sent into Azurill's nightmare and encounter Cresselia where it is revealed that the Partner had been having the same dreams as the Player, as they had been to the erased future. Cresselia attempts to kill them, claiming it is for the greater good, but is interrupted by Drowzee and flees.

A few days later, the Player and Partner are abducted by Palkia and taken to Spacial Rift, where he attempts to execute them for distorting space and time. They escape from him temporarily, only to later encounter him again and defeat him in battle.

Shortly after Palkia is defeated, he is frozen into a nightmare, and a disembodied voice asks the pair if they would like to travel into Palkia's nightmare. When they do, they encounter not only Palkia, but Cresselia as well, who had been the one to inform him about the distortion caused by the Player and Partner. Cresselia attempts once again to kill the pair, but once again is stopped. Another Cresselia appears, telling the Player, Partner and Palkia that the Cresselia that had contacted them in their dreams was actually Darkrai in disguise, who had been attempting to kill the pair so that they could not interfere with his new plans for a world of darkness. Darkrai, enraged that he had failed yet again to kill the pair, flees, telling them to meet him in Dark Crater if they want to stop him.

The Player, Partner, and the real Cresselia comply, traveling to the deepest part of the Dark Crater, where Darkrai attempts to convince the Player and Partner to join him and help him kill Cresselia. The Partner, claiming that they stand no chance against Darkrai anyway, accepts Darkrai's offer, and joins him in attempting to coerce the Player. However, the Player figures out that the Partner has not actually betrayed them, and what they're seeing is actually a nightmare created by Darkrai.

Darkrai then proceeds to summon six minions (Aggron, Arbok, Magmortar, Mismagius, Rhyperior, and Magcargo), and the two parties battle. The Player's group manages to emerge victorious. Despite his loss, Darkrai claims that he has not been defeated, and he opens a Dimensional Hole to try and escape so that he can reattempt his plan during a different time period. Just as Darkrai is about to enter the Dimensional Hole, Palkia appears, and announces that he is there to destroy Darkrai. Darkrai manages to flee through the Dimensional Hole, but Palkia launches an attack (presumably Hyper Beam) at it, shattering the Dimensional Hole with Darkrai in it. Palkia states that Darkrai is not dead, but rather reappeared in some distant corner of the world, likely with amnesia, similar to what happened to the Player when Darkrai attacked them during time travel.

After this, Darkrai can be found in a number of dungeons, provided the player has a Secret Slab or Mystery Part in their inventory, and be potentially recruited.

Super Smash Bros. series
In the Super Smash Bros. series, Darkrai made its debut in Super Smash Bros. Brawl as a collectible trophy.

In Super Smash Bros. for Nintendo 3DS / Wii U and Super Smash Bros. Ultimate, Darkrai can be spawned from a Master Ball or a Poké Ball. Darkrai attacks by using its signature move Dark Void, in which it creates a large dark sphere around itself that puts any opponent that enters it to sleep and deals minor damage to them.

In Super Smash Bros. for Wii U, Darkrai is a red item trophy in Smash Tour. Using it causes a selected opponent to start the battle asleep.

In Super Smash Bros. Ultimate Darkrai is featured as a spirit, which can be obtained either via the Spirit Board or in the World of Light's Dark Realm area. Darkrai is a support spirit, and it grants the fighter equipped with it immunity to falling asleep during battle. Darkrai's spirit battle is against Greninja on the Luigi's Mansion stage with a sleep-inducing floor. Darkrai is summoned from a Poke Ball by the enemy, and only Black Hole items will spawn.

Pokémon Ranger: Shadows of Almia
In Pokémon Ranger: Shadows of Almia, Darkrai is the final boss. While he does not initially appear as a villain, Darkrai must be stopped from engulfing Almia into darkness. Darkrai's power is exploited by Blake Hall, the main antagonist of the game. Blake uses Darkrai and the black crystal that Darkrai protects to fuel his machine. But when a malfunction occurs, Darkrai becomes enraged, becomes even more powerful, and engulfs Blake into a black hole, which was Darkrai's Nightmare technique. However, when the hero uses the power of the red, yellow, and blue crystals collected earlier in the game, Darkrai is able to be stopped.

PokéPark Wii: Pikachu's Adventure
In PokéPark Wii: Pikachu's Adventure, Darkrai is one of the inhabitants of PokéPark.

PokéPark 2: Wonders Beyond
In PokéPark 2: Wonders Beyond, Darkrai is featured as the main antagonist. His desire was to keep all of the Pokémon that lived in the PokéPark in Wish Park because he was lonely.

After Pikachu and his friends defeated Cofagrigus, Darkrai attempted to imprison Pikachu, Oshawott, and Pipkup in the Wish Park. Pikachu and Oshawott were able to escape, but Darkrai captured Piplup.

After Haxorus was defeated by Pikachu and his friends, both he and Hydriegon found out that they were tricked by Gothitelle. Just when they were about to confront her, Darkrai attacks them, knocks them out, and reveals himself to the main heroes. He then ordered Gothitelle to retreat to the final Wish Park zone.

When Pikachu and his friends reached the palace, Darkrai possesses Piplup and convinces him to fight his friends. When Piplup was defeated, he regain full control and ran away. Just then Darkrai, along with Gothitelle, Gothorita, and Gothita teleported in the palace. Darkrai used his powerful psychic abilities and wiped out Snivy's, Tepig's and Oshawott's memories of Pikachu. He then teleported Pikachu into the center of the square. As Pikachu is feeling depressed, Piplup appears and tells him that there's still hope. So Pikachu went towards the Cove Area to find Oshawott, Meadow Area to find Snivy, and the Crag Area to find Tepig, as well as getting their memory back.

After Pikachu found all four of his friends, they went to Wish Park and confronted Darkrai. After he was defeated, Darkrai absorbed all of his power and grew significantly bigger. After being defeated again, Darkrai saw the Dark Vortex. He realized that this was all of his doing, so he decided to sacrifice himself to protect the Wish Park.

Despite Darkrai doing more harm than good, Pikachu and his friends were wondering about Darkrai and if he was still alive, so they went on a search for him. With the help of Reuniclus, Tornadus, Thundurus, Landorus, as well with Reshiram, and Zekrom, they were able to rescue Darkrai. Despite his previous actions, Darkrai was asked by Pikachu and his friends to be his friend. Since they had forgiven Darkrai, he accepted their offers.

Pokkén Tournament / Pokkén Tournament DX
Darkrai appears as a playable character in Pokkén Tournament's arcade version and Pokkén Tournament DX. He is one of the only two Dark-type fighters in the game, the other being Weavile. Darkrai is labeled as a Technical style fighter, using both close and long range Dark attacks. Darkrai can use the move Nightmare, and his burst attack is Infinite Eclipse, in which he causes the target to hallucinate before becoming massive and crushing them in his claws.

Trivia

 * Despite being associated with apparitions, Darkrai is not a Ghost-type.
 * Although Darkrai can travel around in midair, it cannot have the ability Leviate.