Copy Enchantment, Estrid's Invocation, Oblivion Ring, and Altar of the Brood

Prerequisites

• Copy Enchantment in hand
• Estrid's Invocation in hand
• Oblivion Ring on the battlefield
• Altar of the Brood on the battlefield
• available

Steps

1. Cast Estrid's Invocation by paying
2. Estrid's Invocation enters the battlefield, triggering Altar of the Brood and itself
3. Resolve the Altar of Brood trigger, causing each opponent to mill a card
4. Resolve the Estrid's Invocation's trigger, becoming a copy of Oblivion Ring and exiling Oblivion Ring
5. Cast Copy Enchantment by paying
6. Copy Enchantment enters the battlefield, triggering Altar of the Brood and itself
7. Resolve the Altar of Brood trigger, causing each opponent to mill a card
8. Resolve the Copy Enchantment's trigger, becoming a copy of Estrid's Invocation and exiling Estrid's Invocation
9. Estrid's Invocation leaves the battlefield, returning Oblivion Ring from exile to the battlefield
10. Altar of the Brood and Oblivion Ring triggers
11. Resolve the Altar of Brood trigger, causing each opponent to mill a card
12. Resolve the Oblivion Ring's trigger, exiling Copy Enchantment
13. Copy Enchantment leaves the battlefield, returning Estrid's Invocation from exile to the battlefield
14. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB
• Infinite mill