Giant Oyster 
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Creature - Oyster
You may choose not to untap Giant Oyster during your untap step.
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: For as long as Giant Oyster remains tapped, target tapped creature doesn't untap during its controller's untap step, and at the beginning of each of your draw steps, put a -1/-1 counter on that creature. When Giant Oyster leaves the battlefield or becomes untapped, remove all -1/-1 counters from the creature.
0/3