When Junk Diver enters the battlefield, The Sibsig Ceremony triggers, destroying Junk Diver and creating a 2/2 Zombie Druid creature token.
When Junk Diver dies, it triggers, returning Myr Retriever from your graveyard to your hand.
Cast Myr Retriever by paying 0.
When Myr Retriever enters the battlefield, The Sibsig Ceremony triggers, destroying Myr Retriever and creating a 2/2 Zombie Druid creature token.
When Myr Retriever dies, it triggers, returning Junk Diver from your graveyard to your hand.
Repeat.
This ingenious recycling loop turns a pair of cost-reducing engines into an endless creature-crafting factory. The Sibsig Ceremony provides the massive two-mana discount that makes Junk Diver and Myr Retriever completely free to cast, while instantly sacrificing them upon entry to trigger their death abilities. As each scrap-retriever hits the graveyard, it plucks the other right back out of your graveyard to hand, looping indefinitely to flood the board with Zombie Druids. Meanwhile, Honest Rutstein chips in with an extra one-mana discount to help grease the wheels and get your zero-mana loop rolling smoothly.