Guardians of the Tomb (SBCB-ENS06) [Speed Duel: Battle City Box]

During your opponent's Main Phase, when a monster is Special Summoned from your Spell & Trap Zone to your field while you have no cards in your hand, you can draw 1 card, and if you do, you can Set 1 Spell or Trap from your hand. This Skill can only be used once per turn.