Baru, Fist of Krosa

Whenever a Forest enters, green creatures you control get +1/+1 and gain trample until end of turn.
Grandeur — Discard another card named Baru, Fist of Krosa: Create an X/X green Wurm creature token, where X is the number of lands you control.

Aspect of Wolf

Enchant creature
Enchanted creature gets +X/+Y, where X is half the number of Forests you control, rounded down, and Y is half the number of Forests you control, rounded up.

Llanowar Druid

{T}, Sacrifice this creature: Untap all Forests.

Oblivion Stone

{4}, {T}: Put a fate counter on target permanent.
{5}, {T}, Sacrifice this artifact: Destroy each nonland permanent without a fate counter on it, then remove all fate counters from all permanents.

Blanchwood Armor

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

Perilous Vault

{5}, {T}, Exile this artifact: Exile all nonland permanents.

Beacon of Creation

Create a 1/1 green Insect creature token for each Forest you control. Shuffle Beacon of Creation into its owner's library.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Primal Bellow

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

Gaea's Touch

{0}: You may put a basic Forest card from your hand onto the battlefield. Activate only as a sorcery and only once each turn.
Sacrifice this enchantment: Add {G}{G}.

Timber Protector

Other Treefolk creatures you control get +1/+1.
Other Treefolk and Forests you control have indestructible.

Coercive Portal

Will of the council — At the beginning of your upkeep, starting with you, each player votes for carnage or homage. If carnage gets more votes, sacrifice this artifact and destroy all nonland permanents. If homage gets more votes or the vote is tied, draw a card.

Arbor Elf

Ratchet Bomb

{T}: Put a charge counter on this artifact.
{T}, Sacrifice this artifact: Destroy each nonland permanent with mana value equal to the number of charge counters on this artifact.

Ashaya, Soul of the Wild

Ashaya's power and toughness are each equal to the number of lands you control.
Nontoken creatures you control are Forest lands in addition to their other types. (They're still affected by summoning sickness.)

Nissa, Who Shakes the World

Whenever you tap a Forest for mana, add an additional {G}.
+1: Put three +1/+1 counters on up to one target noncreature land you control. Untap it. It becomes a 0/0 Elemental creature with vigilance and haste that's still a land.
−8: You get an emblem with "Lands you control have indestructible." Search your library for any number of Forest cards, put them onto the battlefield tapped, then shuffle.

Utopia Sprawl

Enchant Forest
As this Aura enters, choose a color.
Whenever enchanted Forest is tapped for mana, its controller adds an additional one mana of the chosen color.

Vernal Bloom

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

Three Visits

Search your library for a Forest card, put it onto the battlefield, then shuffle.