Have

Tyranid Prime

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Synapse Creature — Other creatures you control have evolve.

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.

Death's Presence

Whenever a creature you control dies, put X +1/+1 counters on target creature you control, where X is the power of the creature that died.

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.

Harvest Season

Search your library for up to X basic land cards, where X is the number of tapped creatures you control, put those cards onto the battlefield tapped, then shuffle.

Stumpsquall Hydra

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

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.

Jolrael, Mwonvuli Recluse

Whenever you draw your second card each turn, create a 2/2 green Cat creature token.
{4}{G}{G}: Until end of turn, creatures you control have base power and toughness X/X, where X is the number of cards in your hand.

Gargos, Vicious Watcher

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.

Leyline of Abundance

If Leyline of Abundance is in your opening hand, you may begin the game with it on the battlefield.
Whenever you tap a creature for mana, add an additional {G}.
{6}{G}{G}: Put a +1/+1 counter on each creature you control.

Inga and Esika

Creatures you control have vigilance and "{T}: Add one mana of any color. Spend this mana only to cast a creature spell."
Whenever you cast a creature spell, if three or more mana from creatures was spent to cast it, draw a card.

Genestealer Patriarch

Genestealer's Kiss — Whenever Genestealer Patriarch attacks, put an infection counter on target creature defending player controls.
Children of the Cult — Whenever a creature with an infection counter on it dies, you create a token that's a copy of that creature, except it's a Tyranid in addition to its other types.

Broodlord

Ravenous (This creature enters with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.)
Brood Telepathy — When Broodlord enters, distribute X +1/+1 counters among any number of other target creatures you control.

Polukranos, Unchained

Polukranos enters with six +1/+1 counters on it. It escapes with twelve +1/+1 counters on it instead.
If damage would be dealt to Polukranos while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from it.
{1}{B}{G}: Polukranos fights another target creature.
Escape—{4}{B}{G}, Exile six other cards from your graveyard.

Sporocyst

Ravenous (This creature enters with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.)
Defender
Spore Chimney — When Sporocyst enters, search your library for up to X basic land cards, put them onto the battlefield tapped, then shuffle.

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.

Tervigon

Ravenous (This creature enters with X +1/+1 counters on it. If X is 5 or more, draw a card when it enters.)
Trample
Spawn Termagants — Whenever Tervigon deals combat damage to a player, create that many 1/1 green Tyranid creature tokens.

Voracious Hydra

Trample
Voracious Hydra enters with X +1/+1 counters on it.
When Voracious Hydra enters, choose one —
• Double the number of +1/+1 counters on Voracious Hydra.
• Voracious Hydra fights target creature you don't control.

Nylea's Intervention

Choose one —
• Search your library for up to X land cards, reveal them, put them into your hand, then shuffle.
• Nylea's Intervention deals twice X damage to each creature with flying.

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.)

Benevolent Hydra

Benevolent Hydra enters 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.

Protean Hydra

Protean Hydra enters 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.

Stonecoil Serpent

Reach, trample, protection from multicolored
Stonecoil Serpent 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.

Hardened Scales

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.

Malanthrope

Flying
Scavenge the Dead — When Malanthrope enters, exile target player's graveyard. Put a +1/+1 counter on Malanthrope for each creature card exiled this way.

Old One Eye

Trample
Other creatures you control have trample.
When Old One Eye enters, create a 5/5 green Tyranid creature token.
Fast Healing — At the beginning of your first main phase, you may discard two cards. If you do, return Old One Eye from your graveyard to your hand.

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.

Liliana of the Dark Realms

+1: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
−3: Target creature gets +X/+X or -X/-X until end of turn, where X is the number of Swamps you control.
−6: You get an emblem with "Swamps you control have '{T}: Add {B}{B}{B}{B}.'"

Hungering Hydra

Hungering Hydra enters 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.)

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Reverent Hunter

When Reverent Hunter enters, put a number of +1/+1 counters on it equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Bioessence Hydra

Trample
Bioessence Hydra enters with a +1/+1 counter on it for each loyalty counter on planeswalkers you control.
Whenever one or more loyalty counters are put on planeswalkers you control, put that many +1/+1 counters on Bioessence Hydra.

Lictor

Flash
Pheromone Trail — When Lictor enters, if a creature entered the battlefield under an opponent's control this turn, create a 3/3 green Tyranid Warrior creature token with trample.

Casualties of War

Choose one or more —
• Destroy target artifact.
• Destroy target creature.
• Destroy target enchantment.
• Destroy target land.
• Destroy target planeswalker.

Hydra's Growth

Enchant creature
When Hydra's Growth enters, put a +1/+1 counter on enchanted creature.
At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.

Toxicrene

Reach, deathtouch
Hypertoxic Miasma — All lands have "{T}: Add one mana of any color" and lose all other abilities.

Primordial Hydra

Primordial Hydra enters 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.

Yarok, the Desecrated

Deathtouch, lifelink
If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Baleful Strix

Flying, deathtouch
When Baleful Strix enters, draw a card.

Kalonian Hydra

Trample
Kalonian Hydra enters with four +1/+1 counters on it.
Whenever Kalonian Hydra attacks, double the number of +1/+1 counters on each creature you control.

Inscription of Abundance

Kicker {2}{G}
Choose one. If this spell was kicked, choose any number instead.
• Put two +1/+1 counters on target creature.
• Target player gains X life, where X is the greatest power among creatures they control.
• Target creature you control fights target creature you don't control.

Spitting Image

Create a token that's a copy of target creature.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Zopandrel, Hunger Dominus

Reach
At the beginning of each combat, double the power and toughness of each creature you control until end of turn.
{G/P}{G/P}, Sacrifice two other creatures: Put an indestructible counter on Zopandrel, Hunger Dominus. ({G/P} can be paid with either {G} or 2 life.)

Harness Infinity

Exchange your hand and graveyard.
Exile Harness Infinity.

Quandrix Command

Choose two —
• Return target creature or planeswalker to its owner's hand.
• Counter target artifact or enchantment spell.
• Put two +1/+1 counters on target creature.
• Target player shuffles up to three target cards from their graveyard into their library.

Stolen Identity

Create a token that's a copy of target artifact or creature.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Soulquake

Return all creatures on the battlefield and all creature cards in graveyards to their owners' hands.

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

The Ozolith

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.

Glarb, Calamity's Augur

Deathtouch
You may look at the top card of your library any time.
You may play lands and cast spells with mana value 4 or greater from the top of your library.
{T}: Surveil 2.

Bone Sabres

Whenever equipped creature attacks, put four +1/+1 counters on it.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Goldvein Hydra

Vigilance, trample, haste
Goldvein Hydra enters with X +1/+1 counters on it.
When Goldvein Hydra dies, create a number of tapped Treasure tokens 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.

Nexos

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

Fisher's Talent

(Gain the next level as a sorcery to add its ability.)
At the beginning of your upkeep, look at the top card of your library. You may reveal it if it's a land card. Create a 1/1 blue Fish creature token if you revealed it this way. Then draw a card.
{G}{U}: Level 2
If you would create a Fish token, create a 3/3 blue Shark creature token instead.
{2}{G}{U}: Level 3
If you would create a Shark token, create an 8/8 blue Octopus creature token instead.

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.

Briar Hydra

Trample
Domain — Whenever Briar Hydra deals combat damage to a player, put X +1/+1 counters on target creature you control, where X is the number of basic land types among lands you control.

Mind Spring

Managorger Hydra

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

Vraska, Betrayal's Sting

Compleated ({B/P} can be paid with {B} or 2 life. If life was paid, this planeswalker enters with two fewer loyalty counters.)
0: You draw a card and you lose 1 life. Proliferate.
−2: Target creature becomes a Treasure artifact with "{T}, Sacrifice this artifact: Add one mana of any color" and loses all other card types and abilities.
−9: If target player has fewer than nine poison counters, they get a number of poison counters equal to the difference.