Mav Rocco, Demon-touched

Flash
Whenever a creature deals combat damage to you Mav Rocco, Demon-touched becomes a beast
horror until the end of your next turn.
While a beast horror Mav Rocco, Demon-touched gets +4/+4 and has, "Whenever this creature deals combat damage to a player put a +1/+1 counter on all creatures you control and a -1/-1 on all creatures you don't."