Urborg, Tomb of Yawgmoth

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

Apex Altisaur

When this creature enters, it fights up to one target creature you don't control.
Enrage — Whenever this creature is dealt damage, it fights up to one target creature you don't control.

End-Raze Forerunners

Vigilance, trample, haste
When this creature enters, other creatures you control get +2/+2 and gain vigilance and trample until end of turn.

Blightsteel Colossus

Trample, infect, indestructible
If Blightsteel Colossus would be put into a graveyard from anywhere, reveal Blightsteel Colossus and shuffle it into its owner's library instead.

Serra's Emissary

Flying
As this creature enters, choose a card type.
You and creatures you control have protection from the chosen card type.

Prosperous Innkeeper

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Mirkwood Bats

Flying
Whenever you create or sacrifice a token, each opponent loses 1 life.

Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters or dies, you gain 1 life.

Ocelot Pride

First strike, lifelink
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your end step, if you gained life this turn, create a 1/1 white Cat creature token. Then if you have the city's blessing, for each token you control that entered this turn, create a token that's a copy of it.

Soul Warden

Whenever another creature enters, you gain 1 life.

Felidar Sovereign

Vigilance (Attacking doesn't cause this creature to tap.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
At the beginning of your upkeep, if you have 40 or more life, you win the game.

Bilbo, Birthday Celebrant

If you would gain life, you gain that much life plus 1 instead.
{2}{W}{B}{G}, {T}, Exile Bilbo: Search your library for any number of creature cards, put them onto the battlefield, then shuffle. Activate only if you have 111 or more life.

Accomplished Alchemist

{T}: Add one mana of any color.
{T}: Add X mana of any one color, where X is the amount of life you gained this turn.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Rhox Faithmender

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
If you would gain life, you gain twice that much life instead.

Banehound

Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: This artifact deals 50 damage to any target.

Essence Warden

Verdant Sun's Avatar

Whenever this creature or another creature you control enters, you gain life equal to that creature's toughness.

Kambal, Profiteering Mayor

Whenever one or more tokens your opponents control enter, for each of them, create a tapped token that's a copy of it. This ability triggers only once each turn.
Whenever one or more tokens you control enter, each opponent loses 1 life and you gain 1 life.

Crashing Drawbridge

Defender
{T}: Creatures you control gain haste until end of turn.

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.

Primeval Protector

This spell costs {1} less to cast for each creature your opponents control.
When this creature enters, put a +1/+1 counter on each other creature you control.

Yavimaya, Cradle of Growth

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

Command Tower

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

Vault of Champions

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

Rumbleweed

This spell costs {1} less to cast for each land card in your graveyard.
Vigilance, reach, trample
When this creature enters, other creatures you control get +3/+3 and gain trample until end of turn.

Scurry Oak

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever one or more +1/+1 counters are put on this creature, you may create a 1/1 green Squirrel creature token.

Craterhoof Behemoth

Haste
When this creature enters, creatures you control gain trample and get +X/+X until end of turn, where X is the number of creatures you control.

Boon Reflection

If you would gain life, you gain twice that much life instead.

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Elesh Norn, Grand Cenobite

Vigilance
Other creatures you control get +2/+2.
Creatures your opponents control get -2/-2.

Darksteel Splicer

Whenever this creature or another nontoken Phyrexian you control enters, create X 3/3 colorless Phyrexian Golem artifact creature tokens, where X is the number of opponents you have.
Golems you control have indestructible.

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Purity

Flying
If noncombat damage would be dealt to you, prevent that damage. You gain life equal to the damage prevented this way.
When Purity is put into a graveyard from anywhere, shuffle it into its owner's library.

Alhammarret's Archive

If you would gain life, you gain twice that much life instead.
If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Sheoldred, Whispering One

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.
At the beginning of each opponent's upkeep, that player sacrifices a creature of their choice.

Elas il-Kor, Sadistic Pilgrim

Deathtouch
Whenever another creature you control enters, you gain 1 life.
Whenever another creature you control dies, each opponent loses 1 life.

Arcane Signet

Beacon of Immortality

Double target player's life total. Shuffle Beacon of Immortality into its owner's library.

Herd Baloth

Whenever one or more +1/+1 counters are put on this creature, you may create a 4/4 green Beast creature token.

Somberwald Beastmaster

When this creature enters, create a 2/2 green Wolf creature token, a 3/3 green Beast creature token, and a 4/4 green Beast creature token.
Creature tokens you control have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)