Crab Overseer

whenever crab rave ends put a +1 +1 counter on
each crab you control
when crab rave starts put a -1 -1 counter on each
non-crab creature your opponents control
{g/u}{g/u}{g/u} remove all +1 +1 counters from target
crab you control draw cards equal to the number
of +1 +1 counters removed this way