From Bulbapedia, the community-driven Pokémon encyclopedia.
Night Slash is a Dark-type move introduced in Generation IV. It is Physical, ergo it runs off the physical stat.
Night Slash has a critical hit ratio of 12.5%, as opposed to the usual 6.25%.
Night Slash could be a useful move on Absol, as the high critical hit ratio, the 1.5x STAB bonus and Absol's new ability - Strong Luck - can make Night Slash critical hit often, giving it a power of 210.