The Sibsig Ceremony + Scrap Trawler + Workshop Assistant + Gathering Stone

The Sibsig Ceremony

Scrap Trawler

Workshop Assistant

Gathering Stone

How it works

1. Cast Workshop Assistant by paying 0.
2. When Workshop Assistant enters the battlefield, The Sibsig Ceremony triggers, destroying Workshop Assistant and creating a 2/2 Zombie Druid creature token.
3. When Workshop Assistant dies, it triggers, returning Scrap Trawler from your graveyard to your hand.
4. Cast Scrap Trawler by paying 0.
5. When Scrap Trawler enters the battlefield, The Sibsig Ceremony triggers, destroying Scrap Trawler and creating a 2/2 Zombie Druid creature token.
6. When Scrap Trawler dies, it triggers, returning Workshop Assistant from your graveyard to your hand.
7. Repeat.