Duagar, Ceaseless Blade

Double strike
{1}{r/w}: The next time a Warrior creature you
control attacks this turn, put a +1/+1 counter on
each creature you control. You may only activate
this ability as a sorcery and only once per turn.
Remove 5 +1/+1 counters from Duagar: Untap
all creatures you control. After this phase, there
is an additional combat phase.