Efficient Construction + Myr Retriever + Scrap Trawler + Krark-Clan Ironworks

Efficient Construction

Myr Retriever

Scrap Trawler

Krark-Clan Ironworks

How it works

1. Activate Krark-Clan Ironworks by sacrificing Scrap Trawler, adding CC.
2. When Scrap Trawler dies, it triggers, returning Myr Retriever from your graveyard to your hand.
3. Cast Myr Retriever by paying 2.
4. Efficient Construction triggers, creating a 1/1 Thopter artifact creature token.
5. Activate Krark-Clan Ironworks twice by sacrificing the Thopter and Myr Retriever, adding CCCC.
6. When Myr Retriever dies, it triggers, returning Scrap Trawler from your graveyard to your hand.
7. Cast Scrap Trawler by paying 3.
8. Efficient Construction triggers, creating a 1/1 Thopter artifact creature token.
9. Repeat.