Flying

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

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

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

As Primal Clay enters, it becomes your choice of a 3/3 artifact creature, a 2/2 artifact creature with flying, or a 1/6 Wall artifact creature with defender in addition to its other types. (A creature with defender can't attack.)