Pay X Force Choose one of your units with printed build cost X. The chose unit gets Double Damage (Double the damage, after damage prevention, done by this unit.) until end of turn.
Keywords
Double Damage
Double Damage: An isolated, static ability played during the damage placement POP that means, "Put 1 additional damage counter on the defending unit for each 1 damage that wasn't prevented." Damage counters placed by a unit with Double Damage are in addition to the counters that would be placed normally if the attacking unit did not have Double Damage.