Serpent of Yawning Depths

Krakens, Leviathans, Octopuses, and Serpents you control can't be blocked except by Krakens, Leviathans, Octopuses, and Serpents.

Voidslime

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

Ohran Viper

Whenever this creature deals combat damage to a creature, destroy that creature at end of combat.
Whenever this creature deals combat damage to a player, you may draw a card.

Spawning Kraken

Whenever a Kraken, Leviathan, Octopus, or Serpent you control deals combat damage to a player, create a 9/9 blue Kraken creature token.

Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

Fanatic of Rhonas

{T}: Add {G}.
Ferocious — {T}: Add {G}{G}{G}{G}. Activate only if you control a creature with power 4 or greater.
Eternalize {2}{G}{G} ({2}{G}{G}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Snake Druid with no mana cost. Eternalize only as a sorcery.)

Weaver of Harmony

Other enchantment creatures you control get +1/+1.
{G}, {T}: Copy target activated or triggered ability you control from an enchantment source. You may choose new targets for the copy. (Mana abilities can't be targeted.)

Coiling Oracle

When this creature enters, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put that card into your hand.

Prowling Serpopard

This spell can't be countered.
Creature spells you control can't be countered.

Ambush Viper

Entish Restoration

Sacrifice a land. Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle. If you control a creature with power 4 or greater, instead search your library for up to three basic land cards, put them onto the battlefield tapped, then shuffle.

Sakura-Tribe Elder

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

Simic Sky Swallower

Flying, trample
Shroud (This creature can't be the target of spells or abilities.)

Heroic Intervention

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

Ohran Frostfang

Attacking creatures you control have deathtouch.
Whenever a creature you control deals combat damage to a player, draw a card.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Fang of Shigeki

Sosuke, Son of Seshiro

Other Snake creatures you control get +1/+0.
Whenever a Warrior you control deals combat damage to a creature, destroy that creature at end of combat.

Breaching Leviathan

When this creature enters, if you cast it from your hand, tap all nonblue creatures. Those creatures don't untap during their controllers' next untap steps.

Master Biomancer

Each other creature you control enters with a number of additional +1/+1 counters on it equal to this creature's power and as a Mutant in addition to its other types.

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Sakura-Tribe Scout

{T}: You may put a land card from your hand onto the battlefield.

Aesi, Tyrant of Gyre Strait

You may play an additional land on each of your turns.
Landfall — Whenever a land you control enters, you may draw a card.

Broodbirth Viper

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Whenever this creature deals combat damage to a player, you may draw a card.

Winged Coatl

Flash (You may cast this spell any time you could cast an instant.)
Flying
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Counterspell

Imoti, Celebrant of Bounty

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.)
Spells you cast with mana value 6 or greater have cascade.

Sachi, Daughter of Seshiro

Other Snake creatures you control get +0/+1.
Shamans you control have "{T}: Add {G}{G}."

Ice-Fang Coatl

Flash
Flying
When this creature enters, draw a card.
This creature has deathtouch as long as you control at least three other snow permanents.

Ramunap Excavator

Stonecoil Serpent

Reach, trample, protection from multicolored
This creature enters with X +1/+1 counters on it.

Xolatoyac, the Smiling Flood

Whenever Xolatoyac enters or attacks, put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it.
At the beginning of your end step, untap each permanent you control with a counter on it.

Koma, Cosmos Serpent

This spell can't be countered.
At the beginning of each upkeep, create a 3/3 blue Serpent creature token named Koma's Coil.
Sacrifice another Serpent: Choose one —
• Tap target permanent. Its activated abilities can't be activated this turn.
• Koma gains indestructible until end of turn.

Lotus Cobra

Landfall — Whenever a land you control enters, add one mana of any color.

Inkwell Leviathan

Trample
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Shroud (This creature can't be the target of spells or abilities.)

Charix, the Raging Isle

Spells your opponents cast that target Charix cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Koma, World-Eater

This spell can't be countered.
Trample, ward {4}
Whenever Koma deals combat damage to a player, create four 3/3 blue Serpent creature tokens named Koma's Coil.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Yuan-Ti Malison

This creature can't be blocked as long as it's attacking alone.
Whenever this creature deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Lorescale Coatl

Whenever you draw a card, put a +1/+1 counter on this creature.

Sakiko, Mother of Summer

Whenever a creature you control deals combat damage to a player, add that much {G}. Until end of turn, you don't lose this mana as steps and phases end.

Denizen of the Deep

When this creature enters, return each other creature you control to its owner's hand.