The Eternal Tree

At the beginning of your upkeep, put a tree counter on The Eternal Tree.

At the beginning of your first main phase,
create a land token named Eternal Sapling for
each tree counter on The Eternal Tree.
It has, "{t}: Add one {g}to your mana pool for
each tree counter on The Eternal Tree." and
"{g}: Put a tree counter on The Eternal Tree."