Ancient Ziggurat

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

Abraded Bluffs

Abraded Bluffs enters tapped.
When Abraded Bluffs enters, it deals 1 damage to target opponent.
{T}: Add {R} or {W}.

Akoum Refuge enters tapped.
When Akoum Refuge enters, you gain 1 life.
{T}: Add {B} or {R}.

Arctic Flats enters tapped.
{T}: Add {G} or {W}.

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

Blooming Marsh enters tapped unless you control two or fewer other lands.
{T}: Add {B} or {G}.

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {G} or {W}.

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

All Sliver creatures have "Whenever this creature is dealt damage, put a +1/+1 counter on it." (It must survive the damage to get the counter.)

Sliver creatures you control have flying and haste.

Whenever a Sliver deals combat damage to a player, its controller may create a 1/1 colorless Sliver creature token.

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

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

Sliver creatures you control have "When this creature enters, it deals 1 damage to target player or planeswalker and you gain 1 life."

All Slivers have "{T}: Target Sliver creature gets +X/+0 until end of turn, where X is the number of Slivers on the battlefield."

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