In battle, Veil only costs 1 FP to use. The player must press all of the buttons (/) shown on the screen in order to activate it. It allows Vivian to hide Mario underground avoiding an enemy's attack. This technique, however, costs Vivian her next turn leaving only Mario to attack for that turn. This move is useful for avoiding the Shadow Queen's Dark Wave attack and Gloomtail's and Bonetail's Megabreath attack.
Outside of battle, Vivian can hide Mario underground allowing him to spy on certain characters and avoid traps such as the spike trap in Rogueport Sewers. Veil is also needed to find Zip Toad, really Doopliss at the time, in Mario's room and Ghost T. in his room aboard the Excess Express.