You may have Altered Ego enter the battlefield as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.
0 /
0
{X}{G}
Animist's Awakening
Sorcery
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.
{2}
Arcane Signet
Artifact
{T}: Add one mana of any color in your commander's color identity.
{B}{G}
Assassin's Trophy
Instant
Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.
{X}{X}{X}
Astral Cornucopia
Artifact
Astral Cornucopia enters the battlefield with X charge counters on it.
{T}: Choose a color. Add one mana of that color for each charge counter on Astral Cornucopia.
{2}{G}
Beast Within
Instant
Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
{X}{U}{U}{U}
Blue Sun's Zenith
Instant
Target player draws X cards. Shuffle Blue Sun's Zenith into its owner's library.
--
Bojuka Bog
Land
Bojuka Bog enters the battlefield tapped.
When Bojuka Bog enters the battlefield, exile target player's graveyard.
{T}: Add {B}.
{2}{G}
Branching Evolution
Enchantment
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.
{X}{G}
Capricopian
Creature - Goat Hydra
Capricopian enters the battlefield 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.)
0 /
0
{X}{U}
Clash of Wills
Instant
Counter target spell unless its controller pays {X}.
{5}
Clockwork Hydra
Artifact Creature - Hydra
Clockwork Hydra enters the battlefield with four +1/+1 counters on it.
Whenever Clockwork Hydra attacks or blocks, remove a +1/+1 counter from it. If you do, Clockwork Hydra deals 1 damage to any target.
{T}: Put a +1/+1 counter on Clockwork Hydra.
0 /
0
--
Command Tower
Land
{T}: Add one mana of any color in your commander's color identity.
{2}{B}{G}
Corpsejack Menace
Creature - Fungus
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.
4 /
4
{2}{G}
Cultivate
Sorcery
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.
{X}{U}{U}
Curse of the Swine
Sorcery
Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.
{2}{B}{B}
Diabolic Tutor
Sorcery
Search your library for a card, put that card into your hand, then shuffle.
--
Dimir Guildgate
Land - Gate
Dimir Guildgate enters the battlefield tapped.
{T}: Add {U} or {B}.
{2}{G}
Elemental Bond
Enchantment
Whenever a creature with power 3 or greater enters the battlefield under your control, draw a card.
--
Exotic Orchard
Land
{T}: Add one mana of any color that a land an opponent controls could produce.
{X}{B}{B}
Exsanguinate
Sorcery
Each opponent loses X life. You gain life equal to the life lost this way.
{1}{G}
Farseek
Sorcery
Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.
{X}{G}
Feral Hydra
Creature - Hydra Beast
Feral Hydra enters the battlefield with X +1/+1 counters on it.
{3}: Put a +1/+1 counter on Feral Hydra. Any player may activate this ability.
0 /
0
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
{3}{G}{G}{G}
Gargos, Vicious Watcher
Legendary Creature - Hydra
Vigilance
Hydra spells you cast cost {4} less to cast.
Whenever a creature you control becomes the target of a spell, Gargos, Vicious Watcher fights up to one target creature you don't control.
8 /
7
{2}{G}
Garruk's Uprising
Enchantment
When Garruk's Uprising enters the battlefield, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (They can deal excess combat damage to the player or planeswalker they're attacking.)
Whenever a creature with power 4 or greater enters the battlefield under your control, draw a card.
{X}{G}{G}
Genesis Hydra
Creature - Plant 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 the battlefield with X +1/+1 counters on it.
0 /
0
--
Golgari Guildgate
Land - Gate
Golgari Guildgate enters the battlefield tapped.
{T}: Add {B} or {G}.
{G}
Hardened Scales
Enchantment
If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.
--
Hedge Maze
Land - Forest Island
({T}: Add {G} or {U}.)
Hedge Maze enters the battlefield tapped.
When Hedge Maze enters the battlefield, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{3}{U}
Herald of Secret Streams
Creature - Merfolk Warrior
Creatures you control with +1/+1 counters on them can't be blocked.
2 /
3
{3}{G}{G}
Heroes' Bane
Creature - Hydra
Heroes' Bane enters the battlefield with four +1/+1 counters on it.
{2}{G}{G}: Put X +1/+1 counters on Heroes' Bane, where X is its power.
0 /
0
--
Hinterland Harbor
Land
Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.
{5}{G}
Honored Hydra
Creature - Snake Hydra
Trample
Embalm {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Snake Hydra with no mana cost. Embalm only as a sorcery.)
6 /
6
{X}{G}{G}
Hooded Hydra
Creature - Snake Hydra
Hooded Hydra enters the battlefield 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.
0 /
0
{X}{G}
Hungering Hydra
Creature - Hydra
Hungering Hydra enters the battlefield with X +1/+1 counters on it.
Hungering Hydra can't be blocked by more than one creature.
Whenever Hungering Hydra is dealt damage, put that many +1/+1 counters on it. (It must survive the damage to get the counters.)
0 /
0
{2}{G}
Hydra's Growth
Enchantment - Aura
Enchant creature
When Hydra's Growth enters the battlefield, put a +1/+1 counter on enchanted creature.
At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.
{X}{G}{U}
Hydroid Krasis
Creature - Jellyfish Hydra Beast
When you cast this spell, you gain half X life and draw half X cards. Round down each time.
Flying, trample
Hydroid Krasis enters the battlefield with X +1/+1 counters on it.
0 /
0
{X}{U}
Ingenious Prodigy
Creature - Human Wizard
Skulk (This creature can't be blocked by creatures with greater power.)
Ingenious Prodigy enters the battlefield 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.
0 /
1
{2}{G}
Invigorating Surge
Instant
Put a +1/+1 counter on target creature you control, then double the number of +1/+1 counters on that creature.
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
{3}{G}{G}
Kalonian Hydra
Creature - Hydra
Trample
Kalonian Hydra enters the battlefield with four +1/+1 counters on it.
Whenever Kalonian Hydra attacks, double the number of +1/+1 counters on each creature you control.
0 /
0
{X}{B}
Killing Glare
Instant
Destroy target creature with power X or less.
--
Lair of the Hydra
Land
If you control two or more other lands, Lair of the Hydra enters the battlefield tapped.
{T}: Add {G}.
{X}{G}: Until end of turn, Lair of the Hydra becomes an X/X green Hydra creature. It's still a land. X can't be 0.
{X}{G}{G}{G}
Lifeblood Hydra
Creature - Hydra
Trample
Lifeblood Hydra enters the battlefield with X +1/+1 counters on it.
When Lifeblood Hydra dies, you gain life and draw cards equal to its power.
0 /
0
{X}{G}
Mana Bloom
Enchantment
Mana Bloom enters the battlefield with X charge counters on it.
Remove a charge counter from Mana Bloom: Add one mana of any color. Activate only once each turn.
At the beginning of your upkeep, if Mana Bloom has no charge counters on it, return it to its owner's hand.
{2}{G}
Managorger Hydra
Creature - Hydra
Trample
Whenever a player casts a spell, put a +1/+1 counter on Managorger Hydra.
1 /
1
{X}{G}
Mistcutter Hydra
Creature - Hydra
This spell can't be countered.
Haste, protection from blue
Mistcutter Hydra enters the battlefield with X +1/+1 counters on it.
0 /
0
--
Mortuary Mire
Land
Mortuary Mire enters the battlefield tapped.
When Mortuary Mire enters the battlefield, you may put target creature card from your graveyard on top of your library.
{T}: Add {B}.
--
Opulent Palace
Land
Opulent Palace enters the battlefield tapped.
{T}: Add {B}, {G}, or {U}.
--
Path of Ancestry
Land
Path of Ancestry enters the battlefield 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.)
{X}{G}{G}
Primordial Hydra
Creature - Hydra
Primordial Hydra enters the battlefield with X +1/+1 counters on it.
At the beginning of your upkeep, double the number of +1/+1 counters on Primordial Hydra.
Primordial Hydra has trample as long as it has ten or more +1/+1 counters on it.
0 /
0
{X}{B}{B}
Profane Command
Sorcery
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.)
{1}{G}
Rampant Growth
Sorcery
Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
--
Rejuvenating Springs
Land
Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents.
{T}: Add {G} or {U}.
--
Reliquary Tower
Land
You have no maximum hand size.
{T}: Add {C}.
{X}{G}{U}
Repulsive Mutation
Instant
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.
{3}
Simic Cluestone
Artifact
{T}: Add {G} or {U}.
{G}{U}, {T}, Sacrifice Simic Cluestone: Draw a card.
--
Simic Growth Chamber
Land
Simic Growth Chamber enters the battlefield tapped.
When Simic Growth Chamber enters the battlefield, return a land you control to its owner's hand.
{T}: Add {G}{U}.
--
Simic Guildgate
Land - Gate
Simic Guildgate enters the battlefield tapped.
{T}: Add {G} or {U}.
{X}{B}
Slice from the Shadows
Instant
This spell can't be countered. (This includes by the ward ability.)
Target creature gets -X/-X until end of turn.
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{X}{G}{G}
Steelbane Hydra
Creature - Turtle Hydra
Steelbane Hydra enters the battlefield with X +1/+1 counters on it.
{2}{G}, Remove a +1/+1 counter from Steelbane Hydra: Destroy target artifact or enchantment.
0 /
0
{X}{G}{G}{G}
Stumpsquall Hydra
Creature - Hydra
When Stumpsquall Hydra enters the battlefield, distribute X +1/+1 counters among it and any number of commanders.
1 /
1
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Temple of the False God
Land
{T}: Add {C}{C}. Activate only if you control five or more lands.
{X}{G}{U}
The Goose Mother
Legendary Creature - Bird Hydra
Flying
The Goose Mother enters the battlefield with X +1/+1 counters on it.
When The Goose Mother enters the battlefield, create half X Food tokens, rounded up.
Whenever The Goose Mother attacks, you may sacrifice a Food. If you do, draw a card.
2 /
2
{2}
Thought Vessel
Artifact
You have no maximum hand size.
{T}: Add {C}.
{2}{G}
Unbound Flourishing
Enchantment
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.
{X}{G}{G}
Vastwood Hydra
Creature - Hydra
Vastwood Hydra enters the battlefield 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.
0 /
0
{X}{B}{G}{U}
Villainous Wealth
Sorcery
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.
{X}{G}{G}
Voracious Hydra
Creature - Hydra
Trample
Voracious Hydra enters the battlefield with X +1/+1 counters on it.
When Voracious Hydra enters the battlefield, choose one --
• Double the number of +1/+1 counters on Voracious Hydra.
• Voracious Hydra fights target creature you don't control.
0 /
1
{2}{U}{U}
Wave Goodbye
Sorcery
Return each creature without a +1/+1 counter on it to its owner's hand.
{5}{G}
Whiptongue Hydra
Creature - Lizard Hydra
Reach
When Whiptongue Hydra enters the battlefield, destroy all creatures with flying. Put a +1/+1 counter on Whiptongue Hydra for each creature destroyed this way.
4 /
4
{3}
Zagoth Crystal
Artifact
{T}: Add {B}, {G}, or {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)
{1}{B}{G}{U}
Zaxara, the Exemplary
Legendary Creature - Nightmare Hydra
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.
2 /
3
{2}{G}
Cultivate
Sorcery
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.
{2}{G}
Elemental Bond
Enchantment
Whenever a creature with power 3 or greater enters the battlefield under your control, draw a card.
{1}{G}
Farseek
Sorcery
Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.
{2}{G}
Garruk's Uprising
Enchantment
When Garruk's Uprising enters the battlefield, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (They can deal excess combat damage to the player or planeswalker they're attacking.)
Whenever a creature with power 4 or greater enters the battlefield under your control, draw a card.
{5}{G}
Honored Hydra
Creature - Snake Hydra
Trample
Embalm {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Snake Hydra with no mana cost. Embalm only as a sorcery.)
6 /
6
{1}{G}
Rampant Growth
Sorcery
Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
--
Temple of the False God
Land
{T}: Add {C}{C}. Activate only if you control five or more lands.