Underworld Connections

Enchant land
Enchanted land has "{T}, Pay 1 life: Draw a card."

Geyserfield Stalker

Menace (This creature can't be blocked except by two or more creatures.)
Landfall — Whenever a land enters the battlefield under your control, Geyserfield Stalker gets +2/+2 until end of turn.

Scrib Nibblers

{T}: Exile the top card of target player's library. If it's a land card, you gain 1 life.
Landfall — Whenever a land enters the battlefield under your control, you may untap Scrib Nibblers.

Blackblade Reforged

Equipped creature gets +1/+1 for each land you control.
Equip legendary creature {3}
Equip {7}

Dreadwurm

Landfall — Whenever a land enters the battlefield under your control, Dreadwurm gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Hero's Downfall

Tendrils of Corruption

Tendrils of Corruption deals X damage to target creature and you gain X life, where X is the number of Swamps you control.

Swamp

Petrified Field

{T}: Add {C}.
{T}, Sacrifice Petrified Field: Return target land card from your graveyard to your hand.

Lashwrithe

Living weapon (When this Equipment enters the battlefield, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +1/+1 for each Swamp you control.
Equip {B/P}{B/P} ({B/P} can be paid with either {B} or 2 life.)

Sol Ring

Bloodghast

Bloodghast can't block.
Bloodghast has haste as long as an opponent has 10 or less life.
Landfall — Whenever a land enters the battlefield under your control, you may return Bloodghast from your graveyard to the battlefield.

Walking Atlas

{T}: You may put a land card from your hand onto the battlefield.

Tomb Hex

Target creature gets -2/-2 until end of turn.
Landfall — If you had a land enter the battlefield under your control this turn, that creature gets -4/-4 until end of turn instead.

Guildless Commons

Guildless Commons enters the battlefield tapped.
When Guildless Commons enters the battlefield, return a land you control to its owner's hand.
{T}: Add {C}{C}.

Nightshade Harvester

Whenever a land enters the battlefield under an opponent's control, that player loses 1 life. Put a +1/+1 counter on Nightshade Harvester.

Seer's Sundial

Landfall — Whenever a land enters the battlefield under your control, you may pay {2}. If you do, draw a card.

Mutilate

All creatures get -1/-1 until end of turn for each Swamp you control.

Liliana's Shade

When Liliana's Shade enters the battlefield, you may search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
{B}: Liliana's Shade gets +1/+1 until end of turn.

Adventuring Gear

Landfall — Whenever a land enters the battlefield under your control, equipped creature gets +2/+2 until end of turn.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Evolving Wilds

{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Demon's Due

Scry 2, then draw two cards. You lose 2 life.

Bloodgift Demon

Flying
At the beginning of your upkeep, target player draws a card and loses 1 life.

Blood Pact

Target player draws two cards and loses 2 life.

Soul Stair Expedition

Landfall — Whenever a land enters the battlefield under your control, you may put a quest counter on Soul Stair Expedition.
Remove three quest counters from Soul Stair Expedition and sacrifice it: Return up to two target creature cards from your graveyard to your hand.

Nightmare Lash

Equipped creature gets +1/+1 for each Swamp you control.
Equip—Pay 3 life. (Pay 3 life: Attach to target creature you control. Equip only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the creature leaves.)

Slab Hammer

Whenever equipped creature attacks, you may return a land you control to its owner's hand. If you do, the creature gets +2/+2 until end of turn.
Equip {2}

Staff of the Death Magus

Whenever you cast a black spell or a Swamp enters the battlefield under your control, you gain 1 life.

Burnished Hart

{3}, Sacrifice Burnished Hart: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Guul Draz Overseer

Flying
Landfall — Whenever a land enters the battlefield under your control, other creatures you control get +1/+0 until end of turn. If that land is a Swamp, those creatures get +2/+0 until end of turn instead.

Pilgrim's Eye

Flying
When Pilgrim's Eye enters the battlefield, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.

Hedron Rover

Landfall — Whenever a land enters the battlefield under your control, Hedron Rover gets +2/+2 until end of turn.

Damnable Pact

Target player draws X cards and loses X life.

Greed

Sign in Blood

Surrakar Marauder

Landfall — Whenever a land enters the battlefield under your control, Surrakar Marauder gains intimidate until end of turn. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Korlash, Heir to Blackblade

Korlash, Heir to Blackblade's power and toughness are each equal to the number of Swamps you control.
{1}{B}: Regenerate Korlash.
Grandeur — Discard another card named Korlash, Heir to Blackblade: Search your library for up to two Swamp cards, put them onto the battlefield tapped, then shuffle.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Profane Command

Choose two —
• Target player loses X life.
• Return target creature card with mana value X or less from your graveyard to the battlefield.
• Target creature gets -X/-X until end of turn.
• Up to X target creatures gain fear until end of turn. (They can't be blocked except by artifact creatures and/or black creatures.)

Corrupt

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Hagra Crocodile

Hagra Crocodile can't block.
Landfall — Whenever a land enters the battlefield under your control, Hagra Crocodile gets +2/+2 until end of turn.

Expedition Map

{2}, {T}, Sacrifice Expedition Map: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Terramorphic Expanse

{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Consume Spirit

Spend only black mana on X.
Consume Spirit deals X damage to any target and you gain X life.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Myriad Landscape

Myriad Landscape enters the battlefield 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.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Dread Presence

Whenever a Swamp enters the battlefield under your control, choose one —
• You draw a card and you lose 1 life.
• Dread Presence deals 2 damage to any target and you gain 2 life.

Scaretiller

Whenever Scaretiller becomes tapped, choose one —
• You may put a land card from your hand onto the battlefield tapped.
• Return target land card from your graveyard to the battlefield tapped.

Caustic Crawler

Landfall — Whenever a land enters the battlefield under your control, you may have target creature get -1/-1 until end of turn.

Ob Nixilis, the Fallen

Landfall — Whenever a land enters the battlefield under your control, you may have target player lose 3 life. If you do, put three +1/+1 counters on Ob Nixilis, the Fallen.

Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

Skyclave Shade

Kicker {2}{B}
Skyclave Shade can't block.
If Skyclave Shade was kicked, it enters the battlefield with two +1/+1 counters on it.
Landfall — Whenever a land enters the battlefield under your control, if Skyclave Shade is in your graveyard and it's your turn, you may cast it from your graveyard this turn.

Leechridden Swamp

({T}: Add {B}.)
Leechridden Swamp enters the battlefield tapped.
{B}, {T}: Each opponent loses 1 life. Activate only if you control two or more black permanents.

Squelching Leeches

Squelching Leeches's power and toughness are each equal to the number of Swamps you control.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Indulgent Tormentor

Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature or pays 3 life.

Gravepurge

Put any number of target creature cards from your graveyard on top of your library.
Draw a card.

Ghirapur Orrery

Each player may play an additional land on each of their turns.
At the beginning of each player's upkeep, if that player has no cards in hand, that player draws three cards.

Retreat to Hagra

Landfall — Whenever a land enters the battlefield under your control, choose one —
• Target creature gets +1/+0 and gains deathtouch until end of turn.
• Each opponent loses 1 life and you gain 1 life.

Terrain Generator

{T}: Add {C}.
{2}, {T}: You may put a basic land card from your hand onto the battlefield tapped.

Extraplanar Lens

Imprint — When Extraplanar Lens enters the battlefield, you may exile target land you control.
Whenever a land with the same name as the exiled card is tapped for mana, its controller adds one mana of any type that land produced.

Ob Nixilis, the Hate-Twisted

Whenever an opponent draws a card, Ob Nixilis, the Hate-Twisted deals 1 damage to that player.
−2: Destroy target creature. Its controller draws two cards.

Tainted Well

Enchant land
When Tainted Well enters the battlefield, draw a card.
Enchanted land is a Swamp.

Explorer's Scope

Whenever equipped creature attacks, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Solemn Simulacrum

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Infernal Sovereign

Flying, trample
Skip your draw step.
Whenever you play a land or cast a spell, you draw a card and you lose 1 life.