When each turn starts and whenever damage from one of your units causes an opponent's unit to be discarded, add 1 counter to this resource.
Each of your units gets Bounty: Put a mastery counter on this unit.
Remove 1 counter Put a mastery counter on a unit. Play only during your build step.
Remove 3 counters Each of your units gets +1 power for each mastery counter on it until end of turn.