Me and a friend were having a battle, she was using a Meowscarada and never hit a crit on Night Slash. My Dondozo had a Covert Cloak. So, do critical hit boosting moves negate from Covert Cloak?
Covert Cloak protects the holder from the additional effects of other Pokémon's damaging moves.
Covert Cloak (Bulbapedia)
Night Slash isn't listed on the list of moves with additional effects, so it's safe to say Covert Cloak doesn't take critical hit odds into account.