Terrus, Keeper of the Core

This spell can't be countered.
When Terrus enters, destroy target land. At the beginning of each upkeep, gain one mana that the destroyed land could have produced.
You don't lose unspent mana from Terrus as steps
and phases end.
Landfall — Whenever a land enters the battlefield under your control, you may exchange your life total with the amount of unspent mana
from Terrus.