Polukranos, World Eater

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

Assemble the Entmoot

Creatures you control have reach.
Sacrifice this enchantment: Create three tapped X/X green Treefolk creature tokens, where X is the amount of life you gained this turn. Put a reach counter on each of them.

Swallow the Hero Whole

Each player exiles a creature they control. Until the Hydra's next turn, when a Head leaves the battlefield, return the exiled cards to the battlefield under their owners' control.

Lifeblood Hydra

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

Savage Summoning

This spell can't be countered.
The next creature spell you cast this turn can be cast as though it had flash. That spell can't be countered. That creature enters with an additional +1/+1 counter on it.

Ironscale Hydra

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

Heroes' Bane

This creature enters with four +1/+1 counters on it.
{2}{G}{G}: Put X +1/+1 counters on this creature, where X is its power.

Hydra's Impenetrable Hide

Each Head gains indestructible until the end of the Hydra's next turn.

Shrieking Titan Head

At the beginning of the Hydra's end step, each player discards a card.
Hero's Reward — When Shrieking Titan Head leaves the battlefield, each player gains 4 life and draws a card.

Whiptongue Hydra

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

Apex Devastator

Cascade, cascade, cascade, cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order. Multiple instances of cascade each trigger separately.)

Hydra Head

Hero's Reward — When Hydra Head leaves the battlefield, each player gains 2 life.

Mossborn Hydra

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
This creature enters with a +1/+1 counter on it.
Landfall — Whenever a land you control enters, double the number of +1/+1 counters on this creature.

Ravenous Brute Head

Hero's Reward — When Ravenous Brute Head leaves the battlefield, each player gains 2 life and draws a card.

Distract the Hydra

Each player may sacrifice a creature. Each player who sacrificed a creature this way chooses a Head and taps it. Each player who didn't sacrifice a creature loses 3 life.

Naturalize

Noxious Hydra Breath

Choose one — Noxious Hydra Breath deals 5 damage to each player; or destroy each tapped non-Head creature.

Phyrexian Hydra

Honored Hydra

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 this creature becomes monstrous, create X X/X green Hydra creature tokens.

Unified Lunge

Unified Lunge deals X damage to each player, where X is the number of Heads on the battlefield.

Neck Tangle

If there are five or more Heads on the battlefield, tap two of them and they don't untap during the Hydra's next untap step. Otherwise, reveal the top card of the Hydra's library and the Hydra casts that card.

Ramunap Hydra

Vigilance, reach, trample
This creature gets +1/+1 as long as you control a Desert.
This creature gets +1/+1 as long as there is a Desert card in your graveyard.

Beast Within

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

Primal Rage

Creatures you control have trample. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)

Wren's Run Hydra

Reach
This creature 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.)

Snapping Fang Head

At the beginning of the Hydra's end step, Snapping Fang Head deals 1 damage to each player.
Hero's Reward — When Snapping Fang Head leaves the battlefield, each player gains 4 life and draws a card.

Strike the Weak Spot

Destroy target Head. If that Head was elite, the Hydra takes an extra turn after this one.

Primordial Hydra

This creature enters with X +1/+1 counters on it.
At the beginning of your upkeep, double the number of +1/+1 counters on this creature.
This creature has trample as long as it has ten or more +1/+1 counters on it.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on this creature.

Neverwinter Hydra

As this creature 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}.)

Grown from the Stump

Place exactly two cards named Hydra Head onto the battlefield from the Hydra's graveyard. If you can't, reveal cards from the top of the Hydra's library until you reveal a Head card. Put that card onto the battlefield and the rest into the Hydra's graveyard.

Torn Between Heads

Tap up to two Heads. They don't untap during the Hydra's next untap step. Torn Between Heads deals 5 damage to each player.

Case of the Trampled Garden

When this Case enters, distribute two +1/+1 counters among one or two target creatures you control.
To solve — Creatures you control have total power 8 or greater. (If unsolved, solve at the beginning of your end step.)
Solved — Whenever you attack, put a +1/+1 counter on target attacking creature. It gains trample until end of turn.

Nyxborn Hydra

Bestow {X}{G}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
Reach, trample
This permanent enters with X +1/+1 counters on it.
Enchanted creature gets +1/+1 for each +1/+1 counter on this Aura and has reach and trample.

Disorienting Glower

Players can't cast spells until the Hydra's next turn.

Goldvein Hydra

Vigilance, trample, haste
This creature enters with X +1/+1 counters on it.
When this creature dies, create a number of tapped Treasure tokens equal to its power.

Savage Vigor Head

At the beginning of the Hydra's end step, reveal the top card of the Hydra's library and the Hydra casts that card.
Hero's Reward — When Savage Vigor Head leaves the battlefield, each player gains 4 life and draws a card.

Protean Hydra

This creature enters with X +1/+1 counters on it.
If damage would be dealt to this creature, prevent that damage and remove that many +1/+1 counters from it.
Whenever a +1/+1 counter is removed from this creature, put two +1/+1 counters on it at the beginning of the next end step.