Mismagius

It appears as if from nowhere—muttering incantations, placing curses, and giving people terrifying visions.

Mismagius have been known to cast spells to make people fall in love, so some people search for this Pokémon as if their life depended on it.

Feared for its wrath and the curses it spreads, this Pokémon will also, on a whim, cast spells that help people.

Its muttered curses can cause awful headaches or terrifying visions that torment others.

The incantations Mismagius chants can ward against misfortune, so a custom exists of inviting it into one's home. Incur the Pokémon's displeasure, however, and disaster will surely ensue.