Romana II + Overlord of the Hauntwoods + Retreat to Coralhelm + Amulet of Vigor

Romana II

Overlord of the Hauntwoods

Retreat to Coralhelm

Amulet of Vigor

How it works

1. Cast Overlord of the Hauntwoods by paying 3.
2. When Overlord of the Hauntwoods enters the battlefield, it triggers, creating a tapped Everywhere land token.
3. When the Everywhere token enters the battlefield, Amulet of Vigor and Retreat to Coralhelm trigger.
4. Reoslve the Amulet of Vigor trigger, untapping the Everywhere token.
5. Resolve the Retreat to Coralhelm trigger, untapping Romana II.
6. Activate the Everywhere token by tapping it, adding 1.
7. Activate Romana II by paying 1 and tapping it, creating a tapped copy of the Everywhere token.
8. Repeat from step 3.

This clever loop starts by casting Overlord of the Hauntwoods, which drops an Everywhere land token onto the battlefield tapped. Amulet of Vigor immediately steps in to untap that fresh token so it can be tapped for mana, while its entry also triggers Retreat to Coralhelm to untap Romana II. With your mana and your second commander ready to go, Romana II's ability kicks off by paying {1} and tapping to copy that same Everywhere token, which in turn restarts the whole chain of land-entry triggers.