Darkai

Darkrai is known to "inhabit" dreams and causes the target to have unending nightmares, which can be stopped if exposed to a Lunar Feather from Cresselia. However, the "unleashing of nightmares" is actually a defense mechanism, instead of an intentionally malicious act. It can become a shadow and escape danger or contact with humans. It is also capable of some human speech. In The Rise of Darkrai, it was shown its power was weaker than that of Dialga and Palkia. Its relationship to its counterpart, Cresselia, can vary between individuals and canons, with some being antagonistic, as seen Sleepless In Pre-Battle! and Pokémon Mystery Dungeon: Explorers of Time, Darkness, and Sky, or cooperative, as seen in Nightfall? Nightmares! and A Midsummer Night's Light!. As seen in Sleepless In Pre-Battle!, Darkrai does not only cause nightmares; it is also attracted to them. It can also go around objects it is attracted to several times, as seen in the mentioned episode and Pokémon Ranger: Shadows of Almia. Darkrai is said to be active during nights of the new moon. Darkrai possibly feeds off dreams, characterized by its association with never-ending nightmares.

Darkrai is the only known Pokémon capable of learning the move Dark Void.