Explore the Underdark

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.
You take the initiative.

Nexos

Strategic Coordinator — Basic lands you control have "{T}: Add {C}{C}. Spend this mana only on costs that contain {X}."

Dryad's Revival

Return target card from your graveyard to your hand.
Flashback {4}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Environmental Sciences

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. You gain 2 life.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Gaea's Blessing

Target player shuffles up to three target cards from their graveyard into their library.
Draw a card.
When Gaea's Blessing is put into your graveyard from your library, shuffle your graveyard into your library.

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Forest

Perennial Behemoth

You may play lands from your graveyard.
Unearth {G}{G} ({G}{G}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Sylvan Scrying

Search your library for a land card, reveal it, put it into your hand, then shuffle.

Arachnogenesis

Create X 1/2 green Spider creature tokens with reach, where X is the number of creatures attacking you. Prevent all combat damage that would be dealt this turn by non-Spider creatures.

Ancient Greenwarden

Reach (This creature can block creatures with flying.)
You may play lands from your graveyard.
If a land entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Growth Spasm

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this creature: Add {C}."

Sol Ring

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.

Grow from the Ashes

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Search your library for a basic land card, put it onto the battlefield, then shuffle. If this spell was kicked, instead search your library for two basic land cards, put them onto the battlefield, then shuffle.

Emergent Sequence

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. That land becomes a 0/0 green and blue Fractal creature that's still a land. Put a +1/+1 counter on it for each land you had enter the battlefield under your control this turn.

Lightning Greaves

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

Nissa, Who Shakes the World Emblem

Commencement of Festivities

Prevent all combat damage that would be dealt to players this turn.

Ruin in Their Wake

Devoid (This card has no color.)
Search your library for a basic land card and reveal it. You may put that card onto the battlefield tapped if you control a land named Wastes. Otherwise, put that card into your hand. Then shuffle.

Reap and Sow

Choose one —
• Destroy target land.
• Search your library for a land card, put that card onto the battlefield, then shuffle.
Entwine {1}{G} (Choose both if you pay the entwine cost.)

Blunt the Assault

You gain 1 life for each creature on the battlefield. Prevent all combat damage that would be dealt this turn.

Empowered Autogenerator

Empowered Autogenerator enters tapped.
{T}: Put a charge counter on Empowered Autogenerator. Add X mana of any one color, where X is the number of charge counters on Empowered Autogenerator.

Respite

Prevent all combat damage that would be dealt this turn. You gain 1 life for each attacking creature.

Caravan Vigil

Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Morbid — You may put that card onto the battlefield instead of putting it into your hand if a creature died this turn.

Lull

Prevent all combat damage that would be dealt this turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Constant Mists

Buyback—Sacrifice a land. (You may sacrifice a land in addition to any other costs as you cast this spell. If you do, put this card into your hand as it resolves.)
Prevent all combat damage that would be dealt this turn.

Reliquary Tower

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

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

The Initiative

Whenever one or more creatures a player controls deal combat damage to you, that player takes the initiative.
Whenever you take the initiative and at the beginning of your upkeep, venture into Undercity. (If you're in a dungeon, advance to the next room. If you're not, enter Undercity. You can take the initiative even if you already have it.)

Undercity

You can't enter this dungeon unless you "venture into Undercity."
Secret Entrance — Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Leads to: Forge, Lost Well)
Forge — Put two +1/+1 counters on target creature. (Leads to: Trap!, Arena)
Lost Well — Scry 2. (Leads to: Arena, Stash)
Trap! — Target player loses 5 life. (Leads to: Archives)
Arena — Goad target creature. (Leads to: Archives, Catacombs)
Stash — Create a Treasure token. (Leads to: Catacombs)
Archives — Draw a card. (Leads to: Throne of the Dead Three)
Catacombs — Create a 4/1 black Skeleton creature token with menace. (Leads to: Throne of the Dead Three)
Throne of the Dead Three — Reveal the top ten cards of your library. Put a creature card from among them onto the battlefield with three +1/+1 counters on it. It gains hexproof until your next turn. Then shuffle.

Undercity // The Initiative

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Blessed Respite

Target player shuffles their graveyard into their library. Prevent all combat damage that would be dealt this turn.

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Urza's Saga

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Urza's Saga gains "{T}: Add {C}."
II — Urza's Saga gains "{2}, {T}: Create a 0/0 colorless Construct artifact creature token with 'This creature gets +1/+1 for each artifact you control.'"
III — Search your library for an artifact card with mana cost {0} or {1}, put it onto the battlefield, then shuffle.

Spider

Root Snare

Prevent all combat damage that would be dealt this turn.

Edge of Autumn

If you control four or fewer lands, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Cycling—Sacrifice a land. (Sacrifice a land, Discard this card: Draw a card.)

Shigeki, Jukai Visionary

{1}{G}, {T}, Return Shigeki, Jukai Visionary to its owner's hand: Reveal the top four cards of your library. You may put a land card from among them onto the battlefield tapped. Put the rest into your graveyard.
Channel — {X}{X}{G}{G}, Discard Shigeki: Return X target nonlegendary cards from your graveyard to your hand.

Nissa's Renewal

Search your library for up to three basic land cards, put them onto the battlefield tapped, then shuffle. You gain 7 life.

Deep Reconnaissance

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
Flashback {4}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Zendikar Resurgent

Whenever you tap a land for mana, add one mana of any type that land produced. (The types of mana are white, blue, black, red, green, and colorless.)
Whenever you cast a creature spell, draw a card.

Construct

This creature gets +1/+1 for each artifact you control.

Crucible of Worlds

The Tarrasque

The Tarrasque has haste and ward {10} as long as it was cast.
Whenever The Tarrasque attacks, it fights target creature defending player controls.

Boundless Realms

Search your library for up to X basic land cards, where X is the number of lands you control, put them onto the battlefield tapped, then shuffle.

Road of Return

Choose one —
• Return target permanent card from your graveyard to your hand.
• Put your commander into your hand from the command zone.
Entwine {2} (Choose both if you pay the entwine cost.)

Eldrazi Spawn

Glacial Chasm

Cumulative upkeep—Pay 2 life. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
When Glacial Chasm enters, sacrifice a land.
Creatures you control can't attack.
Prevent all damage that would be dealt to you.

Circuitous Route

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Explosive Vegetation

Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Harmonize

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Conduit of Worlds

You may play lands from your graveyard.
{T}: Choose target nonland permanent card in your graveyard. If you haven't cast a spell this turn, you may cast that card. If you do, you can't cast additional spells this turn. Activate only as a sorcery.

Azusa, Lost but Seeking

You may play two additional lands on each of your turns.

Defend the Hearth

Haze of Pollen

Prevent all combat damage that would be dealt this turn.
Cycling {3} ({3}, Discard this card: Draw a card.)

Ramunap Excavator

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Fork in the Road

Search your library for up to two basic land cards and reveal them. Put one into your hand and the other into your graveyard. Then shuffle.

Beneath the Sands

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Cycling {2} ({2}, Discard this card: Draw a card.)

Oracle of Mul Daya

You may play an additional land on each of your turns.
Play with the top card of your library revealed.
You may play lands from the top of your library.

Collective Voyage

Join forces — Starting with you, each player may pay any amount of mana. Each player searches their library for up to X basic land cards, where X is the total amount of mana paid this way, puts them onto the battlefield tapped, then shuffles.

Druid's Deliverance

Prevent all combat damage that would be dealt to you this turn. Populate. (Create a token that's a copy of a creature token you control.)

Druid Class

(Gain the next level as a sorcery to add its ability.)
Landfall — Whenever a land you control enters, you gain 1 life.
{2}{G}: Level 2
You may play an additional land on each of your turns.
{4}{G}: Level 3
When this Class becomes level 3, target land you control becomes a creature with haste and "This creature's power and toughness are each equal to the number of lands you control." It's still a land.

Spellbook

Clinging Mists

Prevent all combat damage that would be dealt this turn.
Fateful hour — If you have 5 or less life, tap all attacking creatures. Those creatures don't untap during their controller's next untap step.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Nissa, Who Shakes the World

Whenever you tap a Forest for mana, add an additional {G}.
+1: Put three +1/+1 counters on up to one target noncreature land you control. Untap it. It becomes a 0/0 Elemental creature with vigilance and haste that's still a land.
−8: You get an emblem with "Lands you control have indestructible." Search your library for any number of Forest cards, put them onto the battlefield tapped, then shuffle.

Jaheira's Respite

Search your library for up to X basic land cards, where X is the number of creatures attacking you, put those cards onto the battlefield tapped, then shuffle.
Prevent all combat damage that would be dealt this turn.

Celebrate the Harvest

Search your library for up to X basic land cards, where X is the number of different powers among creatures you control. Put those cards onto the battlefield tapped, then shuffle.

Thought Vessel

Migration Path

Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.
Cycling {2} ({2}, Discard this card: Draw a card.)

Open the Gates

Search your library for a basic land card or Gate card, reveal it, put it into your hand, then shuffle.

Exploration

You may play an additional land on each of your turns.

Dryad of the Ilysian Grove

You may play an additional land on each of your turns.
Lands you control are every basic land type in addition to their other types.