: At the beginning of your next upkeep, choose a basic land type. Giant Slug gains landwalk of the chosen type until the end of that turn. (It can't be blocked as long as defending player controls a land of that type.)
10/4/2004 If the Slug changes controllers after the mana is spent, the player who activates this ability selects a landwalk during their next upkeep even if they don’t control it at the time.
10/4/2004 When the ability resolves, it creates another ability that triggers at the beginning of your next upkeep. When that ability resolves, you choose a basic land type.