Cloudstone Curio, Dual Nature, Etali, Primal Conqueror // Etali, Primal Sickness, and Leashling

Prerequisites

• Cloudstone Curio on the battlefield
• Dual Nature on the battlefield
• Etali, Primal Conqueror // Etali, Primal Sickness in hand or in the command zone
• Leashling in hand
• plus enough mana to pay for commander tax, if applicable available

Steps

1. Cast Leashling by paying
2. When Leashling enters the battlefield, Dual Nature's first ability triggers, creating a token copy of Leashling
3. Cast Etali either from your hand or from the command zone by paying plus commander tax, if applicable
4. When Etali enters the battlefield, it, Dual Nature's first ability and Cloudstone Curio trigger
5. Resolve the Cloudstone Curio trigger, choosing not to return anything to your hand
6. Resolve the Dual Nature trigger, creating a token copy of Etali
7. Put the token Etali into your graveyard due to the legend rule
8. The token Etali and Cloudstone Curio trigger
9. Resolve the Cloudstone Curio trigger, returning Etali from the battlefield to your hand
10. When Etali leaves the battlefield, Dual Nature's second ability triggers, doing nothing
11. Activate the nontoken Leashling by putting Etali on top of your library from your hand, returning Leashling to your hand from the battlefield
12. When the nontoken Leashling leaves the battlefield, Dual Nature's second ability triggers
13. Holding priority, activate the token Leashling by putting Leashling on top of your library from your hand, returning the token Leashling to your hand from the battlefield
14. Resolve the Dual Nature trigger, doing nothing
15. Resolve the token Etali's trigger from step 8, causing each player to exile cards from the top of their library until they exile a nonland card, and allowing you to cast the nonland cards without paying their mana costs, with you casting Leashling from your library
16. When Leashling enters the battlefield, Dual Nature's first ability triggers, creating a token copy of Leashling
17. Resolve the nontoken Etali's trigger from step 4, causing each player to exile cards from the top of their library until they exile a nonland card, and allowing you to cast the nonland cards without paying their mana costs, with you casting Etali from your library
18. Repeat from step 4

Results

• Cast all nonland cards from each opponent's library
• Exile each opponent's library
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite storm count
• Near-infinite magecraft triggers