Deathrender + Myr Retriever + Workshop Assistant + Grinding Station

Deathrender

Myr Retriever

Workshop Assistant

Grinding Station

How it works

1. Activate Grinding Station by tapping it and sacrificing Myr Retriever.
2. Myr Retriever dies, triggering itself and Deathrender.
3. Resolve the Myr Retriever trigger, returning Workshop Assistant from your graveyard to your hand.
4. Resolve the Deathrender trigger, putting Workshop Assistant from your hand onto the battlefield, and attaching Deathrender to it.
5. Workshop Assistant enters the battlefield, triggering Grinding Station, untapping Grinding Station.
6. Resolve the Grinding Station ability from step 1, causing target player to mill three cards.
7. Activate Grinding Station by tapping it and sacrificing Workshop Assistant.
8. Workshop Assistant dies, triggering itself and Deathrender.
9. Resolve the Workshop Assistant trigger, returning Myr Retriever from your graveyard to your hand.
10. Resolve the Deathrender trigger, putting Myr Retriever from your hand onto the battlefield, and attaching Deathrender to it.
11. Myr Retriever enters the battlefield, triggering Grinding Station, untapping Grinding Station.
12. Resolve the Grinding Station ability from step 7, causing target player to mill three cards.
13. Repeat.