Seedship Broodtender + Phyrexian Altar + Reveillark + Boss's Chauffeur

Seedship Broodtender

Phyrexian Altar

Reveillark

Boss's Chauffeur

How it works

1. Activate Phyrexian Altar by sacrificing Reveillark, adding .
2. When Reveillark dies, it triggers, returning Seedship Broodtender and Boss's Chauffeur from your graveyard to the battlefield. Boss's Chauffeur will enter with a +1/+1 counter on it equal to the number of creatures you control.
3. When Seedship Broodtender enters, it and Boss's Chauffeur trigger.
4. Resolve the Boss's Chauffeur trigger, putting a +1/+1 counter on Boss's Chauffeur.
5. Resolve the Seedship Broodtender trigger, causing you to mill three cards.
6. Activate Phyrexian Altar by sacrificing Boss's Chauffeur, adding .
7. When Boss's Chauffeur dies, it triggers, creating a 1/1 Citizen creature token for each +1/+1 counter on it.
8. Activate Phyrexian Altar three times by sacrificing three Citizens, adding 3.
9. Activate Seedship Broodtender by paying 3 and sacrificing it, returning Reveillark from your graveyard to the battlefield.
10. Repeat.

This intricate loop centers around cycling Reveillark into and out of the graveyard to endlessly recur your board, fueled entirely by the sacrifice outlet Phyrexian Altar. When Reveillark hits the graveyard, its leaves-the-battlefield trigger pulls back both Seedship Broodtender and Boss's Chauffeur, allowing Boss's Chauffeur to grow with counters while Seedship Broodtender fills your graveyard with self-mill. You can then sacrifice Boss's Chauffeur to the Altar to generate a flurry of Citizen tokens, whose own sacrifices provide the exact mana needed to activate Seedship Broodtender's ability and bring Reveillark right back.