Giant Oyster

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.

The activated ability can target only a tapped creature.

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.