Giant Oyster

Creature - Oyster 0/3, 2UU (4)
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.¹
Illus. Nicola Leonard

Gatherer Card Rulings [Nov 2009]

• 10/4/2004: If the Oyster untaps during the draw step before its ability to add a -1/-1 counter resolves, the -1/-1 counter effect resolves and adds a -1/-1 counter after the -1/-1 counters are removed due to being untapped.
• 9/25/2006: The activated ability can target only a tapped creature.
• 9/25/2006: Activating the ability creates a continuous effect that works only as long as Giant Oyster remains tapped, a repeating delayed triggered ability that's in effect only as long as Giant Oyster remains tapped, and a delayed triggered ability that triggers when Giant Oyster untaps or when it leaves the battlefield.
• 9/25/2006: Giant Oyster's ability can be activated during your upkeep, and the creature will get a -1/-1 counter during the draw step that follows it.

Format Legality	Legal in Vintage, Legacy, Extended, MTGO Classic Banned in Standard
Printings (2/15)	Time Spiral "Timeshifted" (Special) Homelands (Uncommon (U3))