The Sibsig Ceremony + Myr Retriever + Junk Diver + The Immortal Sun

The Sibsig Ceremony

Myr Retriever

Junk Diver

The Immortal Sun

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

This clever loop relies on the heavy cost reduction of The Sibsig Ceremony combined with The Immortal Sun to make both Junk Diver and Myr Retriever completely free to cast. When you cast either artifact creature for zero mana, The Sibsig Ceremony immediately destroys it upon entering the battlefield, which conveniently sends it to the graveyard and triggers its death ability. That death trigger allows the fallen automaton to retrieve the *other* artifact creature from your graveyard right back to your hand. You can then cast that second creature for free, where The Sibsig Ceremony destroys it in turn to recover the first, creating an endless, self-sustaining cycle of recursion.