Deathrender + Myr Retriever + Junk Diver + Grinding Station

Deathrender

Myr Retriever

Junk Diver

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 Junk Diver from your graveyard to your hand.
4. Resolve the Deathrender trigger, putting Junk Diver from your hand onto the battlefield, and attaching Deathrender to it.
5. Junk Diver 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 Junk Diver.
8. Junk Diver dies, triggering itself and Deathrender.
9. Resolve the Junk Diver 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.