Cyno, General Mahamatra

Whenever Cyno, General Mahamatra deals combat
damage during your combat phase for the first time
in a turn you may pay {1}{u}{b}{r}. If you do untap
all creatures you control. There is an additional
combat phase after this one.
Cyno, General Mahamatra gains a +1/+1 counter at
the start of every combat phase besides the first one
in every turn.