Clockwork Steed enters with four +1/+0 counters on it.

Clockwork Steed can't be blocked by artifact creatures.

At end of combat, if Clockwork Steed attacked or blocked this combat, remove a +1/+0 counter from it.

, : Put up to X +1/+0 counters on Clockwork Steed. This ability can't cause the total number of +1/+0 counters on Clockwork Steed to be greater than four. Activate only during your upkeep.

You may choose not to untap Giant Oyster during your untap step.

: 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.

Flying

: Roterothopter gets +1/+0 until end of turn. Activate no more than twice each turn.

Defender (This creature can't attack.)

, : Create a 0/1 blue Plant Wall creature token with defender named Kelp.