Creature - Slug 1/1, 1B (2) {5}: 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.1
Illus. Anson Maddocks
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.