Persistent Myr

Whenever you cast a spell, create a 1/1 colorless Myr artifact creature token.

At the beginning of combat on your turn, untap
each Myr you control.

{p/c}{p/u}{p/b}{p/r}{p/g}, {t}: Put three +1/+1 counters on each
Myr you control. Activate only during your turn.