You may choose not to untap Giant Oyster during your untap step.
{T}: 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.
Near Mint - $0.50
Near Mint Non-English - $0.50
Lightly Played - $0.47
Lightly Played Non-English - $0.47
Moderately Played - $0.40
Moderately Played Non-English - $0.40
Heavily Played - $0.30
Heavily Played Non-English - $0.30
Damaged - $0.25
Damaged Non-English - $0.25