Clockwork Courser

Clockwork Steed enters the battlefield with
four +1/+1 counters on it.
Clockwork Steed can't be blocked by artifact creatures.
At end of combat, if Clockwork Courser attacked
or blocked this combat, remove a +1/+1 counter
from it.
{x}{t}: Put up to X +1/+1 counters on Clockwork Courser. This ability can't cause the total number
of +1/+1 counters on Clockwork Courser
to be greater than four.