Dromoka Drillmaster

{w}, {t} : Bolster 1. (Choose a creature with the least toughness among creatures you control and
put one +1/+1 counter on it.)
{1}{w}, {t}, Exert Dromoka Drillmaster:
Bolster 3. (An exerted creature won't untap
during your next untap step.)
"Firm guidance makes bold soldiers."