Romana II + Overlord of the Hauntwoods + Retreat to Coralhelm + Archelos, Lagoon Mystic

Romana II

Overlord of the Hauntwoods

Retreat to Coralhelm

Archelos, Lagoon Mystic

How it works

1. Cast Overlord of the Hauntwoods by paying 3.
2. When Overlord of the Hauntwoods enters the battlefield, it triggers, creating am untapped Everywhere land token due to Archelos.
3. When the Everywhere token enters the battlefield, Retreat to Coralhelm triggers, untapping Romana II.
4. Activate the Everywhere token by tapping it, adding 1.
5. Activate Romana II by paying 1 and tapping it, creating an untapped copy of the Everywhere token due to Archelos.
6. Repeat from step 3.

This loop turns the clever synergy between Overlord of the Hauntwoods and Archelos, Lagoon Mystic into an engine of endless resources. When Overlord of the Hauntwoods enters the battlefield, Archelos, Lagoon Mystic ensures its resulting Everywhere token arrives untapped, immediately triggering Retreat to Coralhelm to untap Romana II. You can then tap that very same Everywhere token for mana and use Romana II to duplicate it, generating an endless stream of copies that continually re-trigger Retreat to Coralhelm to keep the loop going.