Brontes, of the Bolrac

Monstrosity 16 {8}{r}{r}{g}{g} (If this permanent
isn't monstrous, put 16 +1/+1 counters on it and it
becomes monstrous.)
Whenever Brontes, of the Bolrac becomes
monstrous, Brontes fights each creature your opponents control.
If Brontes isn't monstrous, it doesn't untap
during your untap step.