The Sibsig Ceremony + Planar Gate + Junk Diver + Workshop Assistant

The Sibsig Ceremony

Planar Gate

Junk Diver

Workshop Assistant

How it works

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