Darkrai

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

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

To protect itself, it afflicts those around it with nightmares. However, it means no harm.

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

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.