Sidewinder Sliver

All Sliver creatures have flanking. (Whenever a creature without flanking blocks a Sliver, the blocking creature gets -1/-1 until end of turn.)

Syphon Sliver

Sliver creatures you control have lifelink. (Damage dealt by a Sliver creature you control also causes you to gain that much life.)

Forest

Orzhov Guildgate

This land enters tapped.
{T}: Add {W} or {B}.

Crypt Sliver

All Slivers have "{T}: Regenerate target Sliver."

Rakdos Guildgate

This land enters tapped.
{T}: Add {B} or {R}.

Two-Headed Sliver

All Sliver creatures have menace. (They can't be blocked except by two or more creatures.)

Izzet Guildgate

Izzet Guildgate enters tapped.
{T}: Add {U} or {R}.

Telekinetic Sliver

All Slivers have "{T}: Tap target permanent."

Plated Sliver

Selesnya Guildgate

This land enters tapped.
{T}: Add {G} or {W}.

Simic Guildgate

This land enters tapped.
{T}: Add {G} or {U}.

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.)

Plains

Dimir Guildgate

This land enters tapped.
{T}: Add {U} or {B}.

Venom Sliver

Sliver creatures you control have deathtouch. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)

Might Sliver

Crystalline Sliver

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

Winged Sliver

Heart Sliver

Muscle Sliver

Spined Sliver

Whenever a Sliver becomes blocked, that Sliver gets +1/+1 until end of turn for each creature blocking it.

Sentinel Sliver

Sliver creatures you control have vigilance. (Attacking doesn't cause them to tap.)

Gruul Guildgate

This land enters tapped.
{T}: Add {R} or {G}.

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.

Mountain

Swamp

Island

Azorius Guildgate

This land enters tapped.
{T}: Add {W} or {U}.

Manaweft Sliver

Sliver creatures you control have "{T}: Add one mana of any color."

Boros Guildgate

This land enters tapped.
{T}: Add {R} or {W}.

Sliver Legion

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

Golgari Guildgate

This land enters tapped.
{T}: Add {B} or {G}.