Silent Arbiter

No more than one creature can attack each combat.
No more than one creature can block each combat.

Crawlspace

No more than two creatures can attack you each combat.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Soul Conduit

{6}, {T}: Two target players exchange life totals.

Keeper of Progenitus

Whenever a player taps a Mountain, Forest, or Plains for mana, that player adds one mana of any type that land produced.

Helm of Awakening

Fyndhorn Elves

Hypergenesis

Suspend 3—{1}{G}{G}
Starting with you, each player may put an artifact, creature, enchantment, or land card from their hand onto the battlefield. Repeat this process until no one puts a card onto the battlefield.

Lich's Mirror

If you would lose the game, instead shuffle your hand, your graveyard, and all permanents you own into your library, then draw seven cards and your life total becomes 20.

Avenger of Zendikar

When this creature enters, create a 0/1 green Plant creature token for each land you control.
Landfall — Whenever a land you control enters, you may put a +1/+1 counter on each Plant creature you control.

Hall of Gemstone

At the beginning of each player's upkeep, that player chooses a color. Until end of turn, lands tapped for mana produce mana of the chosen color instead of any other color.