This spell can't be countered.

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.

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.

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.

Cast this spell only during the declare blockers step.

X target attacking creatures become blocked. Choking Vines deals 1 damage to each of those creatures. (This spell works on creatures that can't be blocked.)

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.

When Contagion Clasp enters the battlefield, put a -1/-1 counter on target creature.

{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Contortionist Troupe enters the battlefield with X +1/+1 counters on it.

Coven -- At the beginning of your end step, if you control three or more creatures with different powers, put a +1/+1 counter on target creature you control.

You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost.

Counter target spell if its mana value is X.

As Door of Destinies enters the battlefield, choose a creature type.

Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.

Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.

Landfall -- Whenever a land enters the battlefield under your control, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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.

Search your library and/or graveyard for a creature card with mana value X or less and put it onto the battlefield. If you search your library this way, shuffle. If X is 10 or more, creatures you control get +X/+X and gain haste until end of turn.

When Fractal Harness enters the battlefield, create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it and attach Fractal Harness to it.

Whenever equipped creature attacks, double the number of +1/+1 counters on it.

Equip {2}

Populate X times. (To populate, create a token that's a copy of a creature token you control. Do this X times.)

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.

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.

Flying

Whenever Guildpact Informant deals combat damage to a player or planeswalker, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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.

Whenever you cast a spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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

{T}: Add {C}.

{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

This spell costs {G} less to cast for each green creature you control.

Trample

Destroy target creature with power X or less.

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.

When Kiora's Dambreaker enters the battlefield, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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.

Maga, Traitor to Mortals enters the battlefield with X +1/+1 counters on it.

When Maga enters the battlefield, target player loses life equal to the number of +1/+1 counters on it.

Trample

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

Flying

When Merfolk Skydiver enters the battlefield, put a +1/+1 counter on target creature you control.

{3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

This spell can't be countered.

Haste, protection from blue

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

Destroy target artifact or enchantment with mana value X. It can't be regenerated. You gain X life.

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.)

As Neverwinter Hydra enters the battlefield, roll X d6. It enters with a number of +1/+1 counters on it equal to the total of those results.

Trample

Ward {4} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)

Flying

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

+2: Scry 2.

0: Look at the top card of your library. If it's a land card or a creature card with mana value less than or equal to the number of loyalty counters on Nissa, Steward of Elements, you may put that card onto the battlefield.

-6: Untap up to two target lands you control. They become 5/5 Elemental creatures with flying and haste until end of turn. They're still lands.

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.

Choose four. You may choose the same mode more than once.

• Create a 2/2 Citizen creature token that's all colors.

• Return target permanent card from your graveyard to your hand.

• Proliferate.

• You gain 4 life.

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.

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.

Rampant Rejuvenator enters the battlefield with two +1/+1 counters on it.

When Rampant Rejuvenator dies, search your library for up to X basic land cards, where X is Rampant Rejuvenator's power, put them onto the battlefield, then shuffle.

Exile X target cards from a single graveyard.

Flying, trample

When Roalesk, Apex Hybrid enters the battlefield, put two +1/+1 counters on another target creature you control.

When Roalesk dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)

Prevent all combat damage X target creatures would deal this turn.

Destroy target creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Defender (This creature can't attack.)

Whenever Sprouting Phytohydra is dealt damage, you may create a token that's a copy of Sprouting Phytohydra.

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.

Reach, trample, protection from multicolored

Stonecoil Serpent enters the battlefield with X +1/+1 counters on it.

When Stumpsquall Hydra enters the battlefield, distribute X +1/+1 counters among it and any number of commanders.

Flying

Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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

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.

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.

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.

Flying

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

{3}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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.

Cast this spell only during combat on an opponent's turn.

Return X target creature cards from your graveyard to the battlefield. Sacrifice those creatures at the beginning of the next end step.

Wildwood Scourge enters the battlefield 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 Wildwood Scourge.

Reach

Wren's Run Hydra enters the battlefield 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.)

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.