All Legendary Creatures gain Legendary Resistance. They can spend (no Reaction required) to automatically PASS the Contesting Roll. (This is toggled by the controller.)
Some abilities still have effects, like damage, even after a Contesting Roll is successful, resulting in the Target taking half damage.
(This Ability has no charge limit set, and the Legendary Creature can use this as many times as it has Action Point(s) to spend during its Turn.)