Galadriel of Lothlórien + Dryad Arbor + Retreat to Coralhelm + Mortuary + Altar of Dementia

Galadriel of Lothlórien

Dryad Arbor

Retreat to Coralhelm

Mortuary

Altar of Dementia

How it works

1. Play Dryad Arbor.
2. When Dryad Arbor enters the battlefield, Retreat to Coralhelm triggers.
3. Holding priority, activate Altar of Dementia by sacrificing Dryad Arbor.
4. When Dryad Arbor dies, Mortuary triggers, putting Dryad Arbor on top of your library from your graveyard.
5. Resolve the Altar of Dementia ability, causing target player to mill cards equal to Dryad Arbor's power.
6. Resolve the Retreat to Coralhelm trigger from step 2, causing you to scry 1, ensuring to leave Dryad Arbor on top of your library.
7. Galadriel's second ability triggers, causing you to reveal Dryad Arbor from the top of your library, and put it onto the battlefield tapped.
8. Repeat from step 2.