Taiga

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Crystalline Sliver

All Slivers have shroud. (They can't be the targets of spells or abilities.)

Sliver Overlord

{3}: Search your library for a Sliver card, reveal that card, put it into your hand, then shuffle.
{3}: Gain control of target Sliver. (This effect lasts indefinitely.)

Savannah

The First Sliver

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Sliver spells you cast have cascade.

Gaea's Cradle

{T}: Add {G} for each creature you control.

Galerider Sliver

Sliver creatures you control have flying.

Sliver Legion

All Sliver creatures get +1/+1 for each other Sliver on the battlefield.

Tropical Island

Maskwood Nexus

Creatures you control are every creature type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 2/2 blue Shapeshifter creature token with changeling. (It is every creature type.)

Sliver Hivelord

Sliver creatures you control have indestructible. (Damage and effects that say "destroy" don't destroy them.)

Sliver Queen

{2}: Create a 1/1 colorless Sliver creature token.

Fist of Suns

You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.

Striking Sliver

Sliver creatures you control have first strike. (They deal combat damage before creatures without first strike.)

Beast Whisperer

Whenever you cast a creature spell, draw a card.

The Great Henge

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
{T}: Add {G}{G}. You gain 2 life.
Whenever a nontoken creature you control enters, put a +1/+1 counter on it and draw a card.

Bayou

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon, the Boundless enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Cloudshredder Sliver

Sliver creatures you control have flying and haste.

Jodah, Archmage Eternal

Flying
You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.