The top of its body is connected to the lower half by a tiny waist, giving it an hourglass-shaped figure. It has a red spiky growth around its neck and a long white mane flows from its head, obscuring one of its blue eyes. Its thin arms have three claws each, with three spiky protrusions above each elbow. Its shoulders also have long tatters and it appears to be wearing an old ripped cloak or dress. It is able to extend stilt-like extensions to use as "legs". Darkrai resembles a ghost or a haunted spirit. It's appearance suits its ability to give people nightmares.
In Pokémon Mystery Dungeon: Explorers of Time & Explorers of Darkness, Darkrai is the main antagonist of those games. It is found out that Darkrai was the reason that the Hero was turned into a Pokémon and lost his or her memory when he or she had gone back in time with Grovyle to stop the temporal tower from breaking and causing Dialga to turn into Primal Dialga. After the final battle against Darkrai, he attempts to escape in a time portal, when Palkia, who is angered that Darkrai used him, shows up and destroys the time portal as Darkrai is halfway through it, he sustains a lot of damage he loses his memory and gets banished to an unknown place (which is ironic seeing how he was the reason that the hero lost his or her memory.)
Darkrai next appeared in "Sleepless in Pre-Battle", which was its anime debut. It caused nightmares, much like it can in the games. It was concealing itself when Cresselia used its abilities to reveal it from the darkness. The two then battled and Darkrai hid itself once more in the shadows.
In its debut movie "The Rise of Darkrai" Darkrai usually hovers above the ground, but it can sprout long thin legs with which it can walk around like a person.
Another Darkrai appeared under the ownership of a trainer who competed in the Sinnoh League named Tobias in DP episode 183.
In the Pokémon TCG
There is a box set available that includes a deck, booster pack, a Darkrai card, and an oversized version of the Darkrai card. Card Text: It can lull people to sleep and make them dream.
There was also a Japanese card with Darkrai- Darkrai G. It was a DPt-P Promo. It had the Poke-BODY Eerie Aura, and Attack Dark Sleep.
Despite having a ghost image, it is not part Ghost-type.
Darkrai is based on a being of darkness. Each one in the anime so far (Except for The rise of Darkrai one) have incredibly dark natures and can almost be considered evil. However, Darkrai is truly not evil and actually means no harm (as revealed by a mysterious voice after defeating or capturing it on Newmoon Island), as like Lugia, it cannot control its power. Any organic being that goes near it will suffer horrendous nightmares, whether or not Darkrai wills it. Because of this, it chooses to seclude himself on Newmoon Island, similar to how Lugia chose to seclude himself deep in the Whirl Islands/Navel Rock, in order to protect people from its power. However, its power seems to leak into Canalave City due to its close proximity to it.
Darkrai is the final boss in Pokémon Ranger: Shadows of Almia (although the Colossal PokémonRegigigas is fought when all other Pokémon have been caught at least once, however this is not technically considered a final boss).
Darkrai plays the main antagonist in the Pokémon Mystery Dungeon series. After causing the heroes amnesia and transformation of the main hero, in the passage of time, it took control of Dialga. Dialga then only concerned itself with survival, hence the becoming of Primal Dialga. After being foiled, it attempted to trick the world into thinking the hero and partner were responsible for a spatial distortion, which is why Palkia attacked the Hero and his/her partner in Azurill's Dream, nightmares and even tried to attack them in a monster-house style final boss. Darkrai eventually gets amnesia which is ironic.
Darkrai's eyes are similar to the Dawn Stone as it mentions in the description "It sparkles like eyes."
It somewhat resembles Dementors from the Harry Potter series.