Apocalypse Hydra enters the battlefield with X +1/+1 counters on it. If X is 5 or more, it enters the battlefield with an additional X +1/+1 counters on it.

{1}{R}, Remove a +1/+1 counter from Apocalypse Hydra: It deals 1 damage to any target.

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

Basalt Monolith doesn't untap during your untap step.

{T}: Add {C}{C}{C}.

{3}: Untap Basalt Monolith.

Flying

{T}: Add one mana of any color.

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.

({T}: Add {G} or {U}.)

As Breeding Pool enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

{T}: Add {C}.

{1}, {T}: Add one mana of any color.

{4}, {T}, Sacrifice Captivating Cave: Put two +1/+1 counters on target creature. Activate only as a sorcery.

As Cavern of Souls enters the battlefield, choose a creature type.

{T}: Add {C}.

{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Lands you control have "{T}: Add one mana of any color."

{T}: Add one mana of any color.

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

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.

When Court of Garenbrig enters the battlefield, you become the monarch.

At the beginning of your upkeep, distribute two +1/+1 counters among up to two target creatures. Then if you're the monarch, double the number of +1/+1 counters on each creature you control.

When Darigaaz's Caldera enters the battlefield, sacrifice it unless you return a non-Lair land you control to its owner's hand.

{T}: Add {B}, {R}, or {G}.

At the beginning of your upkeep, if an opponent controls three or more creatures, sacrifice Defense of the Heart, search your library for up to two creature cards, put those cards onto the battlefield, then shuffle.

Dragonskull Summit enters the battlefield tapped unless you control a Swamp or a Mountain.

{T}: Add {B} or {R}.

Untap all nonland permanents you control.

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

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

Frontier Bivouac enters the battlefield tapped.

{T}: Add {G}, {U}, or {R}.

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.

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.

{T}: Add three mana of any one color.

Golgari Rot Farm enters the battlefield tapped.

When Golgari Rot Farm enters the battlefield, return a land you control to its owner's hand.

{T}: Add {B}{G}.

Grakmaw, Skyclave Ravager enters the battlefield 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.

Gruul Turf enters the battlefield tapped.

When Gruul Turf enters the battlefield, return a land you control to its owner's hand.

{T}: Add {R}{G}.

Gyrus, Waker of Corpses enters the battlefield with a number of +1/+1 counters on it equal to the amount of mana spent to cast it.

Whenever Gyrus attacks, you may exile target creature card with lesser power from your graveyard. If you do, create a token that's a copy of that card and that's tapped and attacking. Exile the token at end of combat.

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.

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.)

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.

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.)

{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)

When Hydra Broodmaster becomes monstrous, create X X/X green Hydra creature tokens.

Whenever Hydra Omnivore deals combat damage to an opponent, it deals that much damage to each other opponent.

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.

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.

{T}: Add one mana of any type that a land you control could produce. If Incubation Druid has a +1/+1 counter on it, add three mana of that type instead.

{3}{G}{G}: Adapt 3. (If this creature has no +1/+1 counters on it, put three +1/+1 counters on it.)

({T}: Add {W}, {B}, or {G}.)

Indatha Triome enters the battlefield tapped.

Cycling {3} ({3}, Discard this card: Draw a card.)

If a creature would deal combat damage to Ironscale Hydra, prevent that damage and put a +1/+1 counter on Ironscale Hydra.

({T}: Add {U}.)

Imprint -- When Isochron Scepter enters the battlefield, you may exile an instant card with mana value 2 or less from your hand.

{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Jungle Shrine enters the battlefield tapped.

{T}: Add {R}, {G}, or {W}.

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.

({T}: Add {G}, {U}, or {R}.)

Ketria Triome enters the battlefield tapped.

Cycling {3} ({3}, Discard this card: Draw a card.)

As Kindred Discovery enters the battlefield, choose a creature type.

Whenever a creature you control of the chosen type enters the battlefield or attacks, draw a card.

Krosan Verge enters the battlefield tapped.

{T}: Add {C}.

{2}, {T}, Sacrifice Krosan Verge: Search your library for a Forest card and a Plains card, put them onto the battlefield tapped, then shuffle.

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.

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.

At the beginning of your upkeep, flip a coin. If you lose the flip, Mana Crypt deals 3 damage to you.

{T}: Add {C}{C}.

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

Trample

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

Each other creature you control enters the battlefield with a number of additional +1/+1 counters on it equal to Master Biomancer's power and as a Mutant in addition to its other types.

Creatures you control get +1/+1.

Whenever you tap a land for mana, add one mana of any type that land produced.

This spell can't be countered.

Haste, protection from blue

Mistcutter Hydra enters the battlefield with X +1/+1 counters on it.

({T}: Add {R}.)

({T}: Add {R}.)

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Tribute 6 (As this creature enters the battlefield, an opponent of your choice may put six +1/+1 counters on it.)

When Nessian Wilds Ravager enters the battlefield, if tribute wasn't paid, you may have Nessian Wilds Ravager fight another target creature. (Each deals damage equal to its power to the other.)

Opulent Palace enters the battlefield tapped.

{T}: Add {B}, {G}, or {U}.

Trample

Landfall -- Whenever a land enters the battlefield under your control, put a +1/+1 counter on Oran-Rief Hydra. If that land is a Forest, put two +1/+1 counters on Oran-Rief Hydra instead.

({T}: Add {B} or {G}.)

As Overgrown Tomb enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

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.)

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

If damage would be dealt to Phyrexian Hydra, prevent that damage. Put a -1/-1 counter on Phyrexian Hydra for each 1 damage prevented this way.

({T}: Add {W}.)

({T}: Add {W}.)

{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)

When Polukranos, World Eater becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control. Each of those creatures deals damage equal to its power to Polukranos.

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.

Lands you control are every basic land type in addition to their other types.

Protection from everything

If Progenitus would be put into a graveyard from anywhere, reveal Progenitus and shuffle it into its owner's library instead.

Protean Hydra enters the battlefield with X +1/+1 counters on it.

If damage would be dealt to Protean Hydra, prevent that damage and remove that many +1/+1 counters from it.

Whenever a +1/+1 counter is removed from Protean Hydra, put two +1/+1 counters on it at the beginning of the next end step.

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

At the beginning of each player's draw step, that player draws an additional card.

Each player may play an additional land on each of their turns.

When Rith's Grove enters the battlefield, sacrifice it unless you return a non-Lair land you control to its owner's hand.

{T}: Add {R}, {G}, or {W}.

Ward {2}

As Roaming Throne enters the battlefield, choose a creature type.

Roaming Throne is the chosen type in addition to its other types.

If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Sandsteppe Citadel enters the battlefield tapped.

{T}: Add {W}, {B}, or {G}.

Double strike

Savageborn Hydra enters the battlefield with X +1/+1 counters on it.

{1}{R/G}: Put a +1/+1 counter on Savageborn Hydra. Activate only as a sorcery.

Trample

Scourge of Skola Vale enters the battlefield with two +1/+1 counters on it.

{T}, Sacrifice another creature: Put a number of +1/+1 counters on Scourge of Skola Vale equal to the sacrificed creature's toughness.

Seaside Citadel enters the battlefield tapped.

{T}: Add {G}, {W}, or {U}.

As Secluded Courtyard enters the battlefield, choose a creature type.

{T}: Add {C}.

{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type or activate an ability of a creature source of the chosen type.

Cast this spell only during your turn.

Take an extra turn after this one if an opponent cast a blue spell this turn.

Whenever another creature enters the battlefield, its controller may draw a card if its power is greater than each other creature's power.

{G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

{T}: Add {C}{C}.

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.

({T}: Add {R} or {G}.)

As Stomping Ground enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

({T}: Add {B}.)

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

Equip {1}

Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.

At the beginning of combat on your turn, if The Ozolith has counters on it, you may move all counters from The Ozolith onto target creature.

Whenever you cast a spell with mana value 5 or greater, draw a card.

When Treva's Ruins enters the battlefield, sacrifice it unless you return a non-Lair land you control to its owner's hand.

{T}: Add {G}, {W}, or {U}.

Reach

Ulvenwald Hydra's power and toughness are each equal to the number of lands you control.

When Ulvenwald Hydra enters the battlefield, you may search your library for a land card, put it onto the battlefield tapped, then shuffle.

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.

As Unclaimed Territory enters the battlefield, choose a creature type.

{T}: Add {C}.

{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

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.

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.

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.

({T}: Add {B}, {G}, or {U}.)

Zagoth Triome enters the battlefield tapped.

Cycling {3} ({3}, Discard this card: Draw a card.)

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.

({T}: Add {B}, {R}, or {G}.)

Ziatora's Proving Ground enters the battlefield tapped.

Cycling {3} ({3}, Discard this card: Draw a card.)