Clockwork Scorpion

At the beginning of your upkeep, put a +1/+1 counter on Clockwork Scorpion.
Whenever Clockwork Scorpion attacks or blocks, remove a +1/+1 counter from it at end of combat.
Remove five +1/+1 counters from Clockwork Scorpion and exile it: Take an extra turn after this one. Activate this ability only during your first main phase.