The Dusk Ball (ダークボール Dark Ball) a Poké Ball that has a 50% higher chance of catching if it is used at night (8pm-4am) or in a cave. Dusk Ball is also suitable for use as a legendary Pokémon Darkrai, Cresselia and Giratina, Darkrai because it's a Dark type, Cresselia is a Psychic Type, and Giratina lives in a world of darkness and is the Dragon and Ghost type.
3.5x if used in a cave or at night
1x other usage
During Pokémon Diamond and Pearl, the Dusk Ball was called the Dark Ball in Japanese versions, but was renamed as Dusk Ball in English localisations in order to prevent confusion between the two.