Requires

Clever Impersonator must be in hand. Estrid's Invocation must be in hand. Oblivion Ring must be on the battlefield. Altar of the Brood must be on the battlefield. Mana needed:

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 Clever Impersonator by paying .
6. Clever Impersonator 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 Clever Impersonator'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 Clever Impersonator.
13. Clever Impersonator leaves the battlefield, returning Estrid's Invocation from exile to the battlefield.
14. Repeat from step 2.

Results