Cresselia

From the Pokémon Encyclopedia

Cresselia is the Psychic "Lunar Pokémon". She is always female, stands 4'11" tall and weighs 188.7lbs. As she flies, shiny particles cascade from her wings like a veil. She has the Levitate ability; damage-dealing Ground-type moves have no effect on her, she cannot be trapped by Arena Trap, and she takes no damage from Spikes. Her other moves may include Psychic, Charge Beam, Ice Beam, and Calm Mind. Cresselia is a defensive Wall, however its movepool kinda suggest that it is a Special Sweeper. In battle she will try to flee, but Cresselia can be stopped from fleeing by using Mean Look.