Squall Crawler

Overclock 2 (As an additional cost to cast this
creature, you may pay up to 2 {e}. For every {e} paid
this way, this creature enters the battlefield with an additional +1/+1 counter).
{2}, {t}: Put a +1/+1 Counter on Squall Crawler.
When Squall Crawler leaves the battlefield, you
gain {e} equal to its power.