Return target nonland permanent you don't control to its owner's hand. Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Destroy all creatures. They can't be regenerated.

Destroy each nonland permanent with mana value X or less.

Benevolent Hydra enters the battlefield with X +1/+1 counters on it. If one or more +1/+1 counters would be put on another creature you control, that many plus one +1/+1 counters are put on it instead. {T}, Remove a +1/+1 counter from Benevolent Hydra: Put a +1/+1 counter on another target creature you control.

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.

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.

Kurbis, Harvest Celebrant enters the battlefield 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.

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.

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

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}.)

Trample Ochre Jelly enters the battlefield 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 the battlefield with half that many +1/+1 counters on it, rounded down.

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.

{1}{G}{U}: Put a +1/+1 counter on target creature you control. Whenever one or more +1/+1 counters are put on a creature you control, put that many growth counters on Simic Ascendancy. At the beginning of your upkeep, if Simic Ascendancy has twenty or more growth counters on it, you win the game.

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.

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.

Trample, haste If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead. If an opponent would put one or more counters on a permanent or player, they put half that many of each of those kinds of counters on that permanent or player instead, rounded down.

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.

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.

Target player draws X cards. Shuffle Blue Sun's Zenith into its owner's library.

Casualty 3 (As you cast this spell, you may sacrifice a creature with power 3 or greater. When you do, copy this spell.) You draw X cards and you lose X life.

Draw X cards. If X is 10 or more, instead shuffle your graveyard into your library, draw X cards, untap up to five lands, and you have no maximum hand size for the rest of the game. Exile Finale of Revelation.

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.

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.

Draw X cards.

Draw X cards, then discard a card.

At the beginning of each upkeep, if an opponent lost life last turn, put a +1/+1 counter on target creature you control.

Enchant creature {U}: Tap enchanted creature. {U}: Untap enchanted creature.

({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 one mana of any color in your commander's color identity.

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

({T}: Add {G}.)

Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island. {T}: Add {G} or {U}.

({T}: Add {U}.)

{T}, Pay 1 life, Sacrifice Misty Rainforest: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.

({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.

Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents. {T}: Add {G} or {U}.

({T}: Add {B}.)

Undergrowth Stadium enters the battlefield tapped unless you have two or more opponents. {T}: Add {B} or {G}.

{T}, Pay 1 life, Sacrifice Verdant Catacombs: Search your library for a Swamp or Forest card, put it onto the battlefield, then shuffle.

Woodland Cemetery enters the battlefield tapped unless you control a Swamp or a Forest. {T}: Add {B} or {G}.

Genomic Enhancement — {T}: Add one mana of any color. If this mana is spent to cast a creature spell, that creature enters the battlefield with an additional +1/+1 counter on it.

Enchant permanent Enchanted permanent has hexproof. When enchanted permanent leaves the battlefield, if it was historic, draw two cards. (Artifacts, legendaries, and Sagas are historic.)

Permanents you control gain hexproof and indestructible until end of turn.

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.

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.

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.

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

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

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

Vigilance When Topiary Stomper enters the battlefield, search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Topiary Stomper can't attack or block unless you control seven or more lands.

Counter target spell unless its controller pays {X}.

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Destroy target nonland permanent and all other permanents with the same name as that permanent.

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Destroy target artifact or creature. It can't be regenerated.

Choose one — • Destroy target artifact. • Destroy target enchantment. • Exile target card from a graveyard.

Search your library for a card, put that card into your hand, then shuffle.

{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.

Strategic Coordinator — Basic lands you control have "{T}: Add {C}{C}. Spend this mana only on costs that contain {X}."

Arixmethes, Slumbering Isle enters the battlefield tapped with five slumber counters on it. As long as Arixmethes has a slumber counter on it, it's a land. (It's not a creature.) Whenever you cast a spell, you may remove a slumber counter from Arixmethes. {T}: Add {G}{U}.

Deathcap Glade enters the battlefield tapped unless you control two or more other lands. {T}: Add {B} or {G}.

Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)

Reach Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.) As long as Doom Weaver is paired with another creature, each of those creatures has "When this creature dies, draw cards equal to its power."

Copy target creature spell you control, except it isn't legendary if the spell is legendary. (A copy of a creature spell becomes a token.)

Dreamroot Cascade enters the battlefield tapped unless you control two or more other lands. {T}: Add {G} or {U}.

Drowned Catacomb enters the battlefield tapped unless you control an Island or a Swamp. {T}: Add {U} or {B}.

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}.

This spell costs {U}{U}{U} less to cast if an opponent has drawn four or more cards this turn. Draw X cards.

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.

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

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

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.)

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.

Put a +1/+1 counter on target creature you control, then double the number of +1/+1 counters on that creature.

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

Gain control of X target creatures and/or planeswalkers.

{2}: Mirage Mirror becomes a copy of target artifact, creature, enchantment, or land until end of turn.

Morphic Pool enters the battlefield tapped unless you have two or more opponents. {T}: Add {U} or {B}.

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.

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.

Return all nonland permanents target player controls to their owner's hand.

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.

Shipwreck Marsh enters the battlefield tapped unless you control two or more other lands. {T}: Add {U} or {B}.

Put a +1/+1 counter on each of up to X target creatures you control. Auras, Equipment, and modified creatures you control gain hexproof until end of turn. (Equipment, Auras you control, and counters are modifications.)

You may have Spark Double enter the battlefield as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

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

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

When The Meathook Massacre enters the battlefield, each creature gets -X/-X until end of turn. Whenever a creature you control dies, each opponent loses 1 life. Whenever a creature an opponent controls dies, you gain 1 life.

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.

Repeat the following process X times. Each opponent loses 3 life unless that player sacrifices a nonland permanent or discards a card.

Ravenous (This creature enters the battlefield with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.) Shieldwall — Sacrifice Tyrant Guard: Creatures you control with counters on them gain hexproof and indestructible until end of turn.

Target creature you control gets +X/+X and gains hexproof and indestructible until end of turn. (A creature with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

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