
When Michelangelo enters, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.") If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.
How do you want this deck to play?
What the commander does best.
Every +1/+1 counter lands with a bonus one, so your team snowballs faster than a pizza delivery.
786 cards fit this theme
Brew Mutagen and other artifact tokens, then cash them in for counters and artifact payoffs.
186 cards fit this theme
Fill the deck with turtles, ninjas, and mutants, and let the whole sewer crew grow together.
40 cards fit this theme
Off the beaten path, but they work.
Flood the board with tokens, then put extra counters on all of them for a turtle-sized army.
587 cards fit this theme
Turn counters into oversized, trampling monsters that crash through blockers and get rewarded for their power.
421 cards fit this theme