Requires

Copy Enchantment must be in hand. Estrid's Invocation must be in hand. Oblivion Ring must be on the battlefield. Sage of Mysteries must be on the battlefield. Mana needed:

Steps

1. Cast Estrid's Invocation by paying .
2. Estrid's Invocation enters the battlefield, triggering Sage of Mysteries 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 Sage of Mysteries 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. Sage of Mysteries 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