Mal Sueño (Bad Dreams)

Bad Dreams causes all opposing Pokemon that are currently asleep to lose 1/8 of their maximum HP at the end of each turn. This residual damage stacks with other sources of passive damage such as poison, burn, or entry hazards, making sleep an even more punishing status condition.

The ability affects all sleeping opponents simultaneously in double battles, potentially draining multiple targets at once. It applies to any form of sleep, whether induced by moves like Hypnosis and Dark Void or by abilities like Effect Spore. Pokemon using the move Rest are also affected while they remain asleep.

Bad Dreams is the signature ability of Darkrai, the Mythical Dark-type Pokemon introduced in Generation IV. Combined with Darkrai's access to Dark Void and its high Speed stat, Bad Dreams creates a potent strategy of putting opponents to sleep and wearing them down through accumulated passive damage each turn.