You control a nontoken artifact with mana value one or less that can be cast using only colorless mana.
Steps
Activate Krark-Clan Ironworks twice by sacrificing the nontoken artifact with mana value one or less and Myr Retriever, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
When Myr Retriever dies, its ability triggers twice, returning Junk Diver and the nontoken artifact with mana one or less to your hand from your graveyard.
Cast Junk Diver and the nontoken artifact by paying at most ({4} magic symbol) .
Activate Krark-Clan Ironworks twice by sacrificing the nontoken artifact and Junk Diver, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
When Junk Diver dies, it triggers twice, returning the nontoken artifact and Myr Retriever to your hand from your graveyard.
Cast the nontoken artifact and Myr Retriever by paying at most ({3} magic symbol) .