Nidhogg, the Savage Decay

{g}{2}{t}:Draw 2 cards.
{b}{b}{1}{t}:Put a -1/-1 counter on target creature.
Monstrosity 2 (pay {b/g}{3}, put 2 +1/+1 counters on this creature, and it becomes monstrous.)
When Nidhogg, the Savage Decay becomes monstrous, you may exert Nidhogg. If you do, Nidhogg, the Savage Decay has Infect.
(It deals damage in the form of poison counters and -1/-1 counters.)