Miraak, Bound for Life

Indestructible
When Miraak, Bound for Life enters the battlefield, create 3 1/1 black dragon tokens with flying.
{x}{t} Create X 1/1 black dragon tokens with flying.
{x}{b}{b}{t} Destroy X target dragon tokens.
Whenever a dragon creature is destroyed, Miraak,
Bound for Life gains a +1/+1 counter for
each dragon destroyed.