Darkrai

Diamond +2: It can lull people to sleep and make them dream. It is active during nights of the new moon.

Pearl: Folklore has it that on moonless nights, this Pokémon will make people see horrific nightmares.

Platinum +4: To protect itself, it afflicts those around it with nightmares. However, it means no harm.

HeartGold +3: It chases people and Pokémon from its territory by causing them to experience deep, nightmarish slumbers.

Legends: Arceus: On a moonless night, a strange incident occurred in which every one of a village's inhabitants suffered nightmares. The villagers attested that Darkrai appeared before them in these nightmares.