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.

Tempered Sliver

Sliver creatures you control have "Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."

Shadow Sliver

All Sliver creatures have shadow. (They can block or be blocked by only creatures with shadow.)

Ancient Ziggurat

{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Azorius Chancery

Azorius Chancery enters tapped.
When Azorius Chancery enters, return a land you control to its owner's hand.
{T}: Add {W}{U}.

Sliver Hivelord

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

Render Silent

Counter target spell. Its controller can't cast spells this turn.

Island

Sliver Queen

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

Counterspell

Reflex Sliver

Forest

Leeching Sliver

Whenever a Sliver you control attacks, defending player loses 1 life.

Clone Legion

For each creature target player controls, create a token that's a copy of that creature.

Virulent Sliver

All Sliver creatures have poisonous 1. (Whenever a Sliver deals combat damage to a player, that player gets a poison counter. A player with ten or more poison counters loses the game.)

Gemhide Sliver

All Slivers have "{T}: Add one mana of any color."

Sliver Legion

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

Cavern of Souls

As Cavern of Souls enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Diffusion Sliver

Whenever a Sliver creature you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {2}.