Galadriel of Lothlórien + Dryad Arbor + Retreat to Coralhelm + Mortuary + Ashnod's Altar

Galadriel of Lothlórien

Dryad Arbor

Retreat to Coralhelm

Mortuary

Ashnod's Altar

How it works

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

This elegant loop turns the simple land-creature Dryad Arbor into an engine for infinite mana and triggers. Ashnod's Altar provides the sacrifice outlet to generate colorless mana while sending Dryad Arbor to the graveyard, where Mortuary immediately intercepts it to stack it right back on top of your library. From there, Retreat to Coralhelm's landfall trigger gives you the scry 1 needed to set up Galadriel of Lothlórien's second ability, which catches the revealed Dryad Arbor and drops it straight back onto the battlefield.