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.

Winged Sliver

Sliver Queen

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

Unclaimed Territory

As Unclaimed Territory 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.

Mutavault

{T}: Add {C}.
{1}: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.

Sliver Hive

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Sliver spell.
{5}, {T}: Create a 1/1 colorless Sliver creature token. Activate only if you control a Sliver.

Predatory Sliver

Fiery Islet

{T}, Pay 1 life: Add {U} or {R}.
{1}, {T}, Sacrifice Fiery Islet: Draw a card.

Essence Sliver

Whenever a Sliver deals damage, its controller gains that much life.

Muscle Sliver

Sliver Legion

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

Leeching Sliver

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

Sinew Sliver

Cloudshredder Sliver

Sliver creatures you control have flying and haste.

Plains

Striking Sliver

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

Might Sliver

Heart Sliver

Silent Clearing

{T}, Pay 1 life: Add {W} or {B}.
{1}, {T}, Sacrifice Silent Clearing: Draw a card.