Woodland Guidance

Return target card from your graveyard to your hand. Clash with an opponent. If you win, untap all Forests you control. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)
Exile Woodland Guidance.

Vernal Bloom

Whenever a Forest is tapped for mana, its controller adds an additional {G}.

Patron of the Orochi

Snake offering (You may cast this spell any time you could cast an instant by sacrificing a Snake and paying the difference in mana costs between this and the sacrificed Snake. Mana cost includes color.)
{T}: Untap all Forests and all green creatures. Activate only once each turn.

Karametra's Acolyte

{T}: Add an amount of {G} equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Primal Bellow

Target creature gets +1/+1 until end of turn for each Forest you control.

Blanchwood Armor

Enchant creature
Enchanted creature gets +1/+1 for each Forest you control.

Forest

Ranger's Path

Search your library for up to two Forest cards, put them onto the battlefield tapped, then shuffle.

Skyshroud Claim

Search your library for up to two Forest cards, put them onto the battlefield, then shuffle.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Doubling Cube

{3}, {T}: Double the amount of each type of unspent mana you have.

Omnath, Locus of Mana

You don't lose unspent green mana as steps and phases end.
Omnath, Locus of Mana gets +1/+1 for each unspent green mana you have.