Vice will steal items from the party and escape (but not items that cannot be sold or thrown, and if no valid items are available then nothing will be stolen). If they are killed before they escape the item will be returned. If they escape, the item is lost forever.
Although Vice has five attacks, it will only ever use three of them under normal circumstances; Vice will never use the move Seize, and it may only use Hit if under Manipulate or Berserk. It will use Steal and Grind equally, and will use Escape once an item has been stolen from the player.
Beyond stealing items Vice is not a dangerous foe, and can be useful because the player can stealSpeed Drinks from them, the only way to cast Haste until Gongaga.