Ertha Jo, Frontier Mentor, and Aphetto Alchemist

Prerequisites

• Ertha Jo, Frontier Mentor on the battlefield
• Aphetto Alchemist on the battlefield
• Aphetto Alchemist does not have summoning sickness

Steps

1. Activate Aphetto Alchemist by tapping it, targeting itself
2. Ertha Jo's second ability triggers, copying Aphetto Alchemist's ability, targeting any other creature or artifact
3. Resolve both Aphetto Alchemist abilities, untapping it and the other targeted creature or artifact
4. Repeat

Results

• Infinite mana artifacts you control can produce
• Infinite mana creatures you control can produce
• Infinite untap of artifacts you control
• Infinite untap of creatures you control