Otherworldly Battlecry

Put X +1/+1 counters on all Demon creatures you control, then put X red 1/1 Demon tokens with haste onto the battlefield.
During your upkeep, you may pay {2}{b}{r}. If you do, proliferate, then proliferate again.
The battlecry of a herd of oxen is scary, but the battlecry of an angry mob of demons is by far more terrifying.