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As long as this Pokémon is in play against a sleeping opponent, that opponent will take damage equal to 12.5% of its max HP at the end of each turn. This ability will deal damage even if the opponent is asleep due to Rest. In a double battle, if both enemies have Bad Dreams, a sleeping Pokémon will lose health due to Bad Dreams twice. A sleeping Pokémon will not lose health because of its partner's Bad Dreams.