Romana II + Mutable Explorer + Retreat to Coralhelm + Stone-Seeder Hierophant

Romana II

Mutable Explorer

Retreat to Coralhelm

Stone-Seeder Hierophant

How it works

1. Cast Mutable Explorer by paying 2.
2. When Mutable Explorer enters the battlefield, it triggers, creating a tapped Mutavault land token.
3. When the Mutavault token enters the battlefield, Stone-Seeder Hierophant and Retreat to Coralhelm trigger.
4. Reoslve the Stone-Seeder Hierophant trigger, untapping it.
5. Resolve the Retreat to Coralhelm trigger, untapping Romana II.
6. Activate Stone-Seeder Hierophant by tapping it, untapping the Mutavault token.
7. Activate the Mutavault token by tapping it, adding C.
8. Activate Romana II by paying 1 and tapping it, creating a tapped copy of the Mutavault token.
9. Repeat from step 3.

This clever loop begins the moment Mutable Explorer enters the battlefield and drops a fresh Mutavault token, triggering both Retreat to Coralhelm and Stone-Seeder Hierophant simultaneously. With those landfall triggers ironing out our untaps, Stone-Seeder Hierophant's own tap ability can target the very land token that just entered to generate colorless mana. Meanwhile, Romana II steps in as the engine's multiplier, using that mana to churn out endless tapped copies of the token that just entered the battlefield—which in turn fuels further landfall triggers to keep the entire chain spinning indefinitely.