Feroz, Ulgrotha's Warden, Cloudstone Curio, Spark Double, and Clever Impersonator

Prerequisites

• Feroz, Ulgrotha's Warden on the battlefield
• Cloudstone Curio on the battlefield
• Spark Double in hand or on the battlefield or in the library
• Clever Impersonator in hand or in the library

Steps

1. Activate Feroz's second loyalty ability by putting zero loyalty counters on it, causing you to draw a card and put Clever Impersonator from your hand onto the battlefield
2. Choose to have it enter as a copy of Feroz
3. Put Feroz into your graveyard due to the legend rule
4. When Clever Impersonator enters, Cloudstone Curio triggers
5. Choose to return Spark Double to your hand if it's on the battlefield, or nothing to your hand otherwise
6. Activate Clever Impersonator's second ability by putting zero loyalty counters on it, causing you to draw a card and put Spark Double from your hand onto the battlefield
7. Choose to have Spark Double enter as a copy of Clever Impersonator, thus making it a copy of Feroz that isn't legendary
8. When Spark Double enters, Cloudstone Curio triggers, returning Clever Impersonator from the battlefield to your hand
9. Activate Spark Double's second ability by putting zero loyalty counters on it, causing you to draw a card and put Clever Impersonator from your hand onto the battlefield
10. Choose to have Clever Impersonator enter as a copy of Spark Double, thus making it a copy of Feroz that isn't legendary
11. Repeat from step 3

Results

• Infinite card draw
• Infinite draw triggers