Alien Skull (POTD-EN025) [Power of the Duelist]

You can Tribute 1 face-up Level 3 or lower monster on your opponent's side of the field to Special Summon this card to your opponent's side of the field. If you Special Summon this monster this way, place 1 A-Counter on this card, and you cannot Normal Summon or Set the same turn. (If a monster with an A-Counter battles an "Alien" monster, it loses 300 ATK and DEF for each A-Counter during damage calculation only.)