Cheapest priced copy (Homelands): $0.35 at Card Kingdom, near mint, their price list as of .
Giant Oyster 
Creature — Oyster · 0/3 · Special · Time Spiral Timeshifted · #22
You may choose not to untap this creature during your untap step.
{T}: For as long as this creature 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 this creature leaves the battlefield or becomes untapped, remove all -1/-1 counters from the creature.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.35 to $2.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Homelands | 28 | Uncommon | $0.35 | — |
| Time Spiral Timeshifted | 22 | Special | $0.35 | $2.49 |
4 rulings from Wizards of the Coast
- 4 October 2004If 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.
- 25 September 2006Giant 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.
- 25 September 2006The activated ability can target only a tapped creature.
- 25 September 2006Activating 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.