Rayquaza

Flying, Vigilance, Trample, Flash,
{7}{g}: Monstrosity X(Activate this ability only
when you could cast a sorcery. Give this creature X
+1/+1 counters, this may only be used once. Max 5 counters)
This creature costs {x} less to cast. X is equal to
the life you've lost this turn.
This can only attack an opponent with the
highest life. If tied, you decide.