Adarkar Wastes

{T}: Add {C}.
{T}: Add {W} or {U}. This land deals 1 damage to you.

Dark Sphere

{T}, Sacrifice this artifact: The next time a source of your choice would deal damage to you this turn, prevent half that damage, rounded down.

Island

Radstorm

Storm (When you cast this spell, copy it for each spell cast before it this turn.)
Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Archway of Innovation

This land enters tapped unless you control an Island.
{T}: Add {U}.
{U}, {T}: The next spell you cast this turn has improvise. (Your artifacts can help cast that spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Darksteel Citadel

Abandoned Outpost

This land enters tapped.
{T}: Add {W}.
{T}, Sacrifice this land: Add one mana of any color.

Ancient Tomb

{T}: Add {C}{C}. This land deals 2 damage to you.

Aegis of Honor

{1}: The next time an instant or sorcery spell would deal damage to you this turn, that spell deals that damage to its controller instead.

Plains

Azor's Elocutors

At the beginning of your upkeep, put a filibuster counter on this creature. Then if this creature has five or more filibuster counters on it, you win the game.
Whenever a source deals damage to you, remove a filibuster counter from this creature.

Chrome Mox

Imprint — When this artifact enters, you may exile a nonartifact, nonland card from your hand.
{T}: Add one mana of any of the exiled card's colors.

Ancient Den

Show and Tell

Each player may put an artifact, creature, enchantment, or land card from their hand onto the battlefield.

Aegis Turtle

Aether Spellbomb

{U}, Sacrifice this artifact: Return target creature to its owner's hand.
{1}, Sacrifice this artifact: Draw a card.

Aether Vial

At the beginning of your upkeep, you may put a charge counter on this artifact.
{T}: You may put a creature card with mana value equal to the number of charge counters on this artifact from your hand onto the battlefield.

Inexorable Tide

Whenever you cast a spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)