Alesha, Who Smiles at Death + Crystalline Crawler + Aggravated Assault + Arcbound Overseer + Yahenni, Undying Partisan

Alesha, Who Smiles at Death

Crystalline Crawler

Aggravated Assault

Arcbound Overseer

Yahenni, Undying Partisan

How it works

1. Activate Crystalline Crawler's second ability by tapping it, putting a +1/+1 counter on it.
2. Activate Yahenni by sacrificing Arcbound Overseer.
3. When Arcbound Overseer dies, it triggers, putting its +1/+1 counters on Crystalline Crawler.
4. Resolve the Yahenni ability.
5. Activate Crystalline Crawler's first ability five times by removing five +1/+1 counters from it, adding 3.
6. Activate Aggravated Assault by paying 3, causing you to untap all creatures you control and to get an additional combat and main phase after this one.
7. Declare Alesha as an attacker, triggering its ability, targeting Arcbound Overseer.
8. Activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding W/BW/B.
9. Resolve the Alesha trigger, causing you to pay W/BW/B to return Arcbound Overseer from your graveyard to the battlefield tapped and attacking with six +1/+1 counters on it due to its modular ability.
10. Repeat.