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

Copy Enchantment

Estrid's Invocation

Oblivion Ring

Altar of the Brood

How it works

1. Cast Estrid's Invocation by paying 2.
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 2.
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.