Hantengo, Upper Four Demon

If Combat Celebrant hasn’t been exerted this turn, you may exert it as it attacks. When you do, untap all other creatures you control and after this phase, there is an additional combat phase. (An exerted creature won’t untap during your next untap step.)

"I am a monster, and I will destroy everything
in my path. Your pleas and cries are nothing
but a melody to my ears. Witness the true power
of a demon!”