Contested Game Ball

Whenever you're dealt combat damage, the attacking player gains control of this artifact and untaps it.
{2}, {T}: Draw a card and put a point counter on this artifact. Then if it has five or more point counters on it, sacrifice it and create a Treasure token.

Training Center

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Snow-Covered Mountain

Volcanic Island

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, this artifact deals 3 damage to you.
{T}: Add {C}{C}.

Spectator Seating

This land enters tapped unless you have two or more opponents.
{T}: Add {R} or {W}.

Clifftop Retreat

This land enters tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Sea of Clouds

This land enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Sacred Foundry

({T}: Add {R} or {W}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Scalding Tarn

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.

Plateau

Hall of Heliod's Generosity

{T}: Add {C}.
{1}{W}, {T}: Put target enchantment card from your graveyard on top of your library.

Hithlain Rope

This artifact can't be sacrificed.
{1}, {T}: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. The player to your right gains control of this artifact.
{2}, {T}: Draw a card. The player to your right gains control of this artifact.

Sol Ring

Arid Mesa

{T}, Pay 1 life, Sacrifice this land: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Wooded Foothills

{T}, Pay 1 life, Sacrifice this land: Search your library for a Mountain or Forest card, put it onto the battlefield, then shuffle.

Azorius Signet

Flooded Strand

{T}, Pay 1 life, Sacrifice this land: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Mountain

Tundra

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Mystic Monastery

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

Izzet Signet

Snow-Covered Plains

Misty Rainforest

{T}, Pay 1 life, Sacrifice this land: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.

Command Tower

Plains

Sulfur Falls

This land enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Raugrin Triome

({T}: Add {U}, {R}, or {W}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Exotic Orchard

Zedruu the Greathearted

At the beginning of your upkeep, you gain X life and draw X cards, where X is the number of permanents you own that your opponents control.
{U}{R}{W}: Target opponent gains control of target permanent you control.

Windswept Heath

{T}, Pay 1 life, Sacrifice this land: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.

Glacial Fortress

This land enters tapped unless you control a Plains or an Island.
{T}: Add {W} or {U}.

Hallowed Fountain

({T}: Add {W} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Polluted Delta

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Bloodstained Mire

{T}, Pay 1 life, Sacrifice this land: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Island

Marsh Flats

{T}, Pay 1 life, Sacrifice this land: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Snow-Covered Island

Boros Signet

Pendant of Prosperity

This artifact enters under the control of an opponent of your choice.
{2}, {T}: Draw a card, then you may put a land card from your hand onto the battlefield. This artifact's owner draws a card, then that player may put a land card from their hand onto the battlefield.