Flawless Maneuver

If you control a commander, you may cast this spell without paying its mana cost.
Creatures you control gain indestructible until end of turn.

Cultivate

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.

Lifeblood Hydra

Trample
Lifeblood Hydra enters with X +1/+1 counters on it.
When Lifeblood Hydra dies, you gain life and draw cards equal to its power.

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.

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

Hydra Broodmaster

{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.

Lair of the Hydra

If you control two or more other lands, Lair of the Hydra enters 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.

Nature's Lore

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

Forest

Sunpetal Grove

Sunpetal Grove enters tapped unless you control a Forest or a Plains.
{T}: Add {G} or {W}.

Three Visits

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

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.)

Windswept Heath

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

Wren's Run Hydra

Reach
Wren's Run Hydra enters 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.)

Phytohydra

If damage would be dealt to Phytohydra, put that many +1/+1 counters on it instead.

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.

Genesis 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 with X +1/+1 counters on it.

Elementalist's Palette

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}.

Overwhelming Stampede

Until end of turn, creatures you control gain trample and get +X/+X, where X is the greatest power among creatures you control.

Concordant Crossroads

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

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.

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.

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.

Defiler of Vigor

Trample
As an additional cost to cast green permanent spells, you may pay 2 life. Those spells cost {G} less to cast if you paid life this way. This effect reduces only the amount of green mana you pay.
Whenever you cast a green permanent spell, put a +1/+1 counter on each creature you control.

Garruk's Uprising

When this enchantment enters, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever a creature you control with power 4 or greater enters, draw a card.

Hydra Omnivore

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

Steelbane Hydra

Steelbane Hydra enters with X +1/+1 counters on it.
{2}{G}, Remove a +1/+1 counter from Steelbane Hydra: Destroy target artifact or enchantment.

Unnatural Growth

At the beginning of each combat, double the power and toughness of each creature you control until end of turn.

Parallel Lives

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Command Tower

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

Gavony Township

{T}: Add {C}.
{2}{G}{W}, {T}: Put a +1/+1 counter on each creature you control.

Rootborn Defenses

Populate. Creatures you control gain indestructible until end of turn. (To populate, create a token that's a copy of a creature token you control.)

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.

Anointed Procession

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Court of Ardenvale

When Court of Ardenvale enters, you become the monarch.
At the beginning of your upkeep, return target permanent card with mana value 3 or less from your graveyard to your hand. If you're the monarch, return that permanent card to the battlefield instead.

Neverwinter Hydra

As Neverwinter Hydra enters, 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}.)

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.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Nexos

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

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

The Great Henge

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
{T}: Add {G}{G}. You gain 2 life.
Whenever a nontoken creature you control enters, put a +1/+1 counter on it and draw a card.

Polukranos, Engine of Ruin

Reach, lifelink
Whenever Polukranos, Engine of Ruin or another nontoken Hydra you control dies, create a 3/3 green and white Phyrexian Hydra creature token with reach and a 3/3 green and white Phyrexian Hydra creature token with lifelink.

Polukranos Reborn

Reach
{6}{W/P}: Transform Polukranos Reborn. Activate only as a sorcery. ({W/P} can be paid with either {W} or 2 life.)

Polukranos Reborn // Polukranos, Engine of Ruin

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Vorinclex, Monstrous Raider

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.

Elemental Bond

Whenever a creature you control with power 3 or greater enters, draw a card.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Rampant Rejuvenator

Rampant Rejuvenator enters 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.

Managorger Hydra

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

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Temple Garden

({T}: Add {G} or {W}.)
As Temple Garden enters, you may pay 2 life. If you don't, it enters tapped.

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.

Ironscale Hydra

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

Sol Ring

Canopy Vista

({T}: Add {G} or {W}.)
Canopy Vista enters tapped unless you control two or more basic lands.

Karn's Bastion

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

Herald's Horn

As Herald's Horn enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Triumph of the Hordes

Until end of turn, creatures you control get +1/+1 and gain trample and infect. (Creatures with infect deal damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Cavern of Souls

As Cavern of Souls enters, 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.

Garenbrig Growth

Return target creature or land card from your graveyard to your hand. (Then exile this card. You may cast the enchantment later from exile.)

Virtue of Strength

If you tap a basic land for mana, it produces three times as much of that mana instead.

Virtue of Strength // Garenbrig Growth

Mistcutter Hydra

This spell can't be countered.
Haste, protection from blue
Mistcutter Hydra enters with X +1/+1 counters on it.

Overgrown Farmland

Overgrown Farmland enters tapped unless you control two or more other lands.
{T}: Add {G} or {W}.

Inspiring Call

Draw a card for each creature you control with a +1/+1 counter on it. Those creatures gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

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.)

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.)

Urza's Incubator

As Urza's Incubator enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Kodama's Reach

Plains

Whiptongue Hydra

Reach
When Whiptongue Hydra enters, destroy all creatures with flying. Put a +1/+1 counter on Whiptongue Hydra for each creature destroyed this way.

Heroic Intervention

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

Rampant Growth

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

Arcane Signet

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.

Greater Good

Sacrifice a creature: Draw cards equal to the sacrificed creature's power, then discard three cards.

Ancient Tomb

{T}: Add {C}{C}. Ancient Tomb deals 2 damage to you.

Bountiful Promenade

Bountiful Promenade enters tapped unless you have two or more opponents.
{T}: Add {G} or {W}.

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.

Ulvenwald Hydra

Reach
Ulvenwald Hydra's power and toughness are each equal to the number of lands you control.
When Ulvenwald Hydra enters, you may search your library for a land card, put it onto the battlefield tapped, then shuffle.

Shamanic Revelation

Draw a card for each creature you control.
Ferocious — You gain 4 life for each creature you control with power 4 or greater.