Open the Way

X can't be greater than the number of players in the game.
Reveal cards from the top of your library until you reveal X land cards. Put those land cards onto the battlefield tapped and the rest on the bottom of your library in a random order.

Ancient Lumberknot

Each creature you control with toughness greater than its power assigns combat damage equal to its toughness rather than its power.

Slaughter the Strong

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Sun-Dappled Celebrant

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Vigilance

Arcane Signet

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

Tree of Perdition

Defender
{T}: Exchange target opponent's life total with this creature's toughness.

Unhallowed Phalanx

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Swamp

The Necrobloom

Landfall — Whenever a land you control enters, create a 0/1 green Plant creature token. If you control seven or more lands with different names, create a 2/2 black Zombie creature token instead.
Land cards in your graveyard have dredge 2. (You may return a land card from your graveyard to your hand and mill two cards instead of drawing a card.)

Reach
Whenever Six attacks, mill three cards. You may put a land card from among them into your hand.
During your turn, nonland permanent cards in your graveyard have retrace. (You may cast permanent cards from your graveyard by discarding a land card in addition to paying their other costs.)

Plains

Sapling Nursery

Affinity for Forests (This spell costs {1} less to cast for each Forest you control.)
Landfall — Whenever a land you control enters, create a 3/4 green Treefolk creature token with reach.
{1}{G}, Exile this enchantment: Treefolk and Forests you control gain indestructible until end of turn.

Fecund Greenshell

Reach
As long as you control ten or more lands, creatures you control get +2/+2.
Whenever this creature or another creature you control with toughness greater than its power enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. Otherwise, put it into your hand.

Jaws of Defeat

Whenever a creature you control enters, target opponent loses life equal to the difference between that creature's power and its toughness.

Temple Garden

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

Spry and Mighty

Choose two creatures you control. You draw X cards and the chosen creatures get +X/+X and gain trample until end of turn, where X is the difference between the chosen creatures' powers.

Expel the Interlopers

Choose a number between 0 and 10. Destroy all creatures with power greater than or equal to the chosen number.

Command Tower

Assault Formation

Each creature you control assigns combat damage equal to its toughness rather than its power.
{G}: Target creature with defender can attack this turn as though it didn't have defender.
{2}{G}: Creatures you control get +0/+1 until end of turn.

Crystal Barricade

Defender (This creature can't attack.)
You have hexproof. (You can't be the target of spells or abilities your opponents control.)
Prevent all noncombat damage that would be dealt to other creatures you control.

Arbor Adherent

{T}: Add one mana of any color.
{T}: Add X mana of any one color, where X is the greatest toughness among other creatures you control.

Ferrafor, Young Yew

When Ferrafor enters, create a number of 1/1 green Saproling creature tokens equal to the number of counters among creatures target player controls.
{T}: Double the number of each kind of counter on target creature.

Sandsteppe Citadel

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

Sol Ring

Doran, Besieged by Time

Each creature spell you cast with toughness greater than its power costs {1} less to cast.
Whenever a creature you control attacks or blocks, it gets +X/+X until end of turn, where X is the difference between its power and toughness.