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 of your library in a random order. Multiple instances of cascade each trigger separately.)

Whenever you cast a creature spell, draw a card.

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

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.

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

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.

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

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 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.

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.

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

As an additional cost to cast this spell, sacrifice a creature. You draw cards equal to the sacrificed creature's power, then you gain life equal to its toughness.

Strive — This spell costs {G} more to cast for each target beyond the first. Until end of turn, any number of target creatures each get +1/+1 and gain "{T}: This creature fights another target creature."

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