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.)

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.

Jodah, Archmage Eternal

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

Sliver Legion

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

Savannah

Fist of Suns

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

Crystalline Sliver

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

Striking Sliver

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

Gaea's Cradle

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

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.

Galerider Sliver

Sliver creatures you control have flying.

Taiga

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.)

Bayou

Tropical Island

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.

Cloudshredder Sliver

Sliver creatures you control have flying and haste.

Yavimaya, Cradle of Growth

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

Sliver Hivelord

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