Spell Proof Armor (SBSC-ENS02) - Speed Duel: Scars of Battle 1st Edition

Activate this Skill during your Main Phase. All Machine monsters you control are unaffected by your opponent's Spell effects. You can Normal Summon Machine Normal Monsters with 1 less Tribute. If a non-Machine monster is in your GY, flip this Skill over. This Skill can only be used once per Duel.