Mockingbird

Flying
You may have Mockingbird enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast Mockingbird, except it's a Bird in addition to its other types and it has flying.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Golgari Rot Farm

Golgari Rot Farm enters tapped.
When Golgari Rot Farm enters, return a land you control to its owner's hand.
{T}: Add {B}{G}.

Steelbane Hydra

Steelbane Hydra enters with X +1/+1 counters on it.
{2}{G}, Remove a +1/+1 counter from Steelbane Hydra: Destroy target artifact or enchantment.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Erebos's Intervention

Choose one —
• Target creature gets -X/-X until end of turn. You gain X life.
• Exile up to twice X target cards from graveyards.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on Managorger Hydra.

Dismal Backwater

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {B}.

Unbound Flourishing

Whenever you cast a permanent spell with a mana cost that contains {X}, double the value of X.
Whenever you cast an instant or sorcery spell or activate an ability, if that spell's mana cost or that ability's activation cost contains {X}, copy that spell or ability. You may choose new targets for the copy.

Black Sun's Twilight

Up to one target creature gets -X/-X until end of turn. If X is 5 or more, return a creature card with mana value X or less from your graveyard to the battlefield tapped.

Walking Ballista

Walking Ballista enters with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.

Vastwood Hydra

Vastwood Hydra enters with X +1/+1 counters on it.
When Vastwood Hydra dies, you may distribute a number of +1/+1 counters equal to the number of +1/+1 counters on Vastwood Hydra among any number of creatures you control.

Endless One

Endless One enters with X +1/+1 counters on it.

Thran Dynamo

Evolving Wilds

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

Grakmaw, Skyclave Ravager

Grakmaw, Skyclave Ravager enters with three +1/+1 counters on it.
Whenever another creature you control dies, if it had a +1/+1 counter on it, put a +1/+1 counter on Grakmaw.
When Grakmaw dies, create an X/X black and green Hydra creature token, where X is the number of +1/+1 counters on Grakmaw.

Path of Ancestry

Path of Ancestry enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Thornwood Falls

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {G} or {U}.

Rite of Consumption

As an additional cost to cast this spell, sacrifice a creature.
Rite of Consumption deals damage equal to the sacrificed creature's power to target player or planeswalker. You gain life equal to the damage dealt this way.

Overwhelming Stampede

Until end of turn, creatures you control gain trample and get +X/+X, where X is the greatest power among creatures you control.

Hooded Hydra

Hooded Hydra enters with X +1/+1 counters on it.
When Hooded Hydra dies, create a 1/1 green Snake creature token for each +1/+1 counter on it.
Morph {3}{G}{G}
As Hooded Hydra is turned face up, put five +1/+1 counters on it.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Swamp

Villainous Wealth

Target opponent exiles the top X cards of their library. You may cast any number of spells with mana value X or less from among them without paying their mana costs.

Icy Blast

Tap X target creatures.
Ferocious — If you control a creature with power 4 or greater, those creatures don't untap during their controllers' next untap steps.

Kurbis, Harvest Celebrant

Kurbis, Harvest Celebrant enters with a number of +1/+1 counters on it equal to the amount of mana spent to cast it.
Remove a +1/+1 counter from Kurbis: Prevent all damage that would be dealt this turn to another target creature with a +1/+1 counter on it.

Nimbus Swimmer

Flying
Nimbus Swimmer enters with X +1/+1 counters on it.

Inspiring Call

Draw a card for each creature you control with a +1/+1 counter on it. Those creatures gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Mind Spring

Wren's Run Hydra

Reach
Wren's Run Hydra enters with X +1/+1 counters on it.
Reinforce X—{X}{G}{G} ({X}{G}{G}, Discard this card: Put X +1/+1 counters on target creature.)

Hydroid Krasis

When you cast this spell, you gain half X life and draw half X cards. Round down each time.
Flying, trample
Hydroid Krasis enters with X +1/+1 counters on it.

Mistcutter Hydra

This spell can't be countered.
Haste, protection from blue
Mistcutter Hydra enters with X +1/+1 counters on it.

Rampaging Yao Guai

Vigilance, trample
Rampaging Yao Guai enters with X +1/+1 counters on it.
When Rampaging Yao Guai enters, destroy any number of target artifacts and/or enchantments with total mana value X or less.

Pull from Tomorrow

Jungle Hollow

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {B} or {G}.

Dregs of Sorrow

Destroy X target nonblack creatures. Draw X cards.

Vorel of the Hull Clade

{G}{U}, {T}: Double the number of each kind of counter on target artifact, creature, or land.

Sol Ring

Lifeblood Hydra

Trample
Lifeblood Hydra enters with X +1/+1 counters on it.
When Lifeblood Hydra dies, you gain life and draw cards equal to its power.

Branching Evolution

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead.

Repulsive Mutation

Put X +1/+1 counters on target creature you control. Then counter up to one target spell unless its controller pays mana equal to the greatest power among creatures you control.

Fellwar Stone

Arcane Signet

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

Jiang Yanggu, Wildcrafter

Each creature you control with a +1/+1 counter on it has "{T}: Add one mana of any color."
−1: Put a +1/+1 counter on target creature.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Duskshell Crawler

When Duskshell Crawler enters, put a +1/+1 counter on target creature.
Each creature you control with a +1/+1 counter on it has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.)

Zaxara, the Exemplary

Deathtouch
{T}: Add two mana of any one color.
Whenever you cast a spell with {X} in its mana cost, create a 0/0 green Hydra creature token, then put X +1/+1 counters on it.

Feral Hydra

Feral Hydra enters with X +1/+1 counters on it.
{3}: Put a +1/+1 counter on Feral Hydra. Any player may activate this ability.

Capricopian

Capricopian enters with X +1/+1 counters on it.
{2}: Put a +1/+1 counter on Capricopian, then you may reselect which player Capricopian is attacking. Only the player Capricopian is attacking may activate this ability and only during the declare attackers step. (It can't attack its controller.)

Nyxborn Hydra

Bestow {X}{G}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
Reach, trample
Nyxborn Hydra enters with X +1/+1 counters on it.
Enchanted creature gets +1/+1 for each +1/+1 counter on Nyxborn Hydra and has reach and trample.

Kiora, Behemoth Beckoner

Whenever a creature you control with power 4 or greater enters, draw a card.
−1: Untap target permanent.

Corpsejack Menace

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on it instead.

Island

Dimir Aqueduct

Dimir Aqueduct enters tapped.
When Dimir Aqueduct enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Slice from the Shadows

This spell can't be countered. (This includes by the ward ability.)
Target creature gets -X/-X until end of turn.

Distorting Wake

Return X target nonland permanents to their owners' hands.

Forest

Winding Constrictor

If one or more counters would be put on an artifact or creature you control, that many plus one of each of those kinds of counters are put on that permanent instead.
If you would get one or more counters, you get that many plus one of each of those kinds of counters instead.

Stonecoil Serpent

Reach, trample, protection from multicolored
Stonecoil Serpent enters with X +1/+1 counters on it.

Ivy Elemental

Ivy Elemental enters with X +1/+1 counters on it.

Command Tower

Death Wind

Target creature gets -X/-X until end of turn.

Genesis Hydra

When you cast this spell, reveal the top X cards of your library. You may put a nonland permanent card with mana value X or less from among them onto the battlefield. Then shuffle the rest into your library.
Genesis Hydra enters with X +1/+1 counters on it.

The Goose Mother

Flying
The Goose Mother enters with X +1/+1 counters on it.
When The Goose Mother enters, create half X Food tokens, rounded up.
Whenever The Goose Mother attacks, you may sacrifice a Food. If you do, draw a card.

Opulent Palace

Opulent Palace enters tapped.
{T}: Add {B}, {G}, or {U}.

Terramorphic Expanse

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

Elementalist's Palette

Whenever you cast a spell with {X} in its mana cost, put two charge counters on Elementalist's Palette.
{T}: Add one mana of any color.
{T}: Add {C} for each charge counter on Elementalist's Palette. Spend this mana only on costs that contain {X}.

Suffer the Past

Exile X target cards from target player's graveyard. For each card exiled this way, that player loses 1 life and you gain 1 life.

Ingenious Prodigy

Skulk (This creature can't be blocked by creatures with greater power.)
Ingenious Prodigy enters with X +1/+1 counters on it.
At the beginning of your upkeep, if Ingenious Prodigy has one or more +1/+1 counters on it, you may remove a +1/+1 counter from it. If you do, draw a card.

Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Animist's Awakening

Reveal the top X cards of your library. Put all land cards from among them onto the battlefield tapped and the rest on the bottom of your library in a random order.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, untap those lands.

Syncopate

Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Wildwood Scourge

This creature enters with X +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on another non-Hydra creature you control, put a +1/+1 counter on this creature.

Condescend

Counter target spell unless its controller pays {X}. Scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Simic Growth Chamber

Simic Growth Chamber enters tapped.
When Simic Growth Chamber enters, return a land you control to its owner's hand.
{T}: Add {G}{U}.

Gadwick, the Wizened

When Gadwick, the Wizened enters, draw X cards.
Whenever you cast a blue spell, tap target nonland permanent an opponent controls.

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.)

Ochre Jelly

Trample
Ochre Jelly enters with X +1/+1 counters on it.
Split — When Ochre Jelly dies, if it had two or more +1/+1 counters on it, create a token that's a copy of it at the beginning of the next end step. The token enters with half that many +1/+1 counters on it, rounded down.

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.