The Watcher in the Water

The Watcher in the Water enters tapped with nine stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Whenever you draw a card during an opponent's turn, create a 1/1 blue Tentacle creature token.
Whenever a Tentacle you control dies, untap up to one target Kraken and put a stun counter on up to one target nonland permanent.

Reliquary Tower

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

Simic Signet

Scuttling Sentinel

Flash
Vigilance
When Scuttling Sentinel enters, put a +1/+1 counter on another target creature you control. Until end of turn, that creature becomes a blue Crab in addition to its other types and gains hexproof. (It can't be the target of spells or abilities your opponents control.)

Talisman of Curiosity

{T}: Add {C}.
{T}: Add {G} or {U}. Talisman of Curiosity deals 1 damage to you.

Replicated Ring

Snap

Return target creature to its owner's hand. Untap up to two lands.

Thriving Isle

Thriving Isle enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Mystic Genesis

Counter target spell. Create an X/X green Ooze creature token, where X is that spell's mana value.

Whale

When this creature dies, create a 9/9 blue Kraken creature token.

Plant

Deepchannel Mentor

Blue creatures you control can't be blocked.

Three Tree City

As Three Tree City enters, choose a creature type.
{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to the number of creatures you control of the chosen type.

Rogue's Passage

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

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Arbor Elf

Beast

Illusion

Whenever this creature blocks a creature, that creature doesn't untap during its controller's next untap step.

Geometric Nexus

Whenever a player casts an instant or sorcery spell, put a number of charge counters on Geometric Nexus equal to that spell's mana value.
{6}, {T}, Remove all charge counters from Geometric Nexus: Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is the number of charge counters removed this way.

Master Biomancer

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

Sol Ring

Deekah, Fractal Theorist

Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is that spell's mana value.
{3}{U}: Target creature token can't be blocked this turn.

Esika's Chariot

When Esika's Chariot enters, create two 2/2 green Cat creature tokens.
Whenever Esika's Chariot attacks, create a token that's a copy of target token you control.
Crew 4

Battlefront Krushok

Battlefront Krushok can't be blocked by more than one creature.
Each creature you control with a +1/+1 counter on it can't be blocked by more than one creature.

Curiosity Crafter

Flying
You have no maximum hand size.
Whenever a creature token you control deals combat damage to a player, draw a card.

Unsubstantiate

Return target spell or creature to its owner's hand.

Merfolk

Unwind

Counter target noncreature spell. Untap up to three lands.

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.

Rewind

Counter target spell. Untap up to four lands.

Progenitor Mimic

You may have Progenitor Mimic enter as a copy of any creature on the battlefield, except it has "At the beginning of your upkeep, if this creature isn't a token, create a token that's a copy of this creature."

Crafty Cutpurse

Flash
When Crafty Cutpurse enters, each token that would be created under an opponent's control this turn is created under your control instead.

Plasm Capture

Counter target spell. At the beginning of your next first main phase, add X mana in any combination of colors, where X is that spell's mana value.

Combine Chrysalis

Creature tokens you control have flying.
{2}{G}{U}, {T}, Sacrifice a token: Create a 4/4 green Beast creature token. Activate only as a sorcery.

Fish

When this creature dies, create a 6/6 blue Whale creature token with "When this creature dies, create a 9/9 blue Kraken creature token."

Breaching Leviathan

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

Avenger of Zendikar

When Avenger of Zendikar enters, create a 0/1 green Plant creature token for each land you control.
Landfall — Whenever a land you control enters, you may put a +1/+1 counter on each Plant creature you control.

Archmage's Charm

Choose one —
• Counter target spell.
• Target player draws two cards.
• Gain control of target nonland permanent with mana value 1 or less.

Mesmerizing Benthid

When Mesmerizing Benthid enters, create two 0/2 blue Illusion creature tokens with "Whenever this creature blocks a creature, that creature doesn't untap during its controller's next untap step."
Mesmerizing Benthid has hexproof as long as you control an Illusion.

Old-Growth Dryads

When Old-Growth Dryads enters, each opponent may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

Irenicus's Vile Duplication

Create a token that's a copy of target creature you control, except the token has flying and it isn't legendary.

Esix, Fractal Bloom

Flying
The first time you would create one or more tokens during each of your turns, you may instead choose a creature other than Esix, Fractal Bloom and create that many tokens that are copies of that creature.

Fractal

Kiora's Follower

Lord of Atlantis

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Lullmage Mentor

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.
Tap seven untapped Merfolk you control: Counter target spell.

Tentacle

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.

Kitchen

Kitchen enters tapped.
{T}: Add {G} or {U}.
{4}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Reservoir Kraken

Trample, ward {2}
At the beginning of each combat, if Reservoir Kraken is untapped, any opponent may tap an untapped creature they control. If they do, tap Reservoir Kraken and create a 1/1 blue Fish creature token with "This creature can't be blocked."

Simic Guildgate

This land enters tapped.
{T}: Add {G} or {U}.

Clue

{2}, Sacrifice this artifact: Draw a card.

Eureka Moment

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

Treasure

{T}, Sacrifice this artifact: Add one mana of any color.

Tempest Caller

When Tempest Caller enters, tap all creatures target opponent controls.

Topiary Panther

Trample
Basic landcycling {1}{G} ({1}{G}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Replicating Ring

{T}: Add one mana of any color.
At the beginning of your upkeep, put a night counter on Replicating Ring. Then if it has eight or more night counters on it, remove all of them and create eight colorless snow artifact tokens named Replicated Ring with "{T}: Add one mana of any color."

Adrix and Nev, Twincasters

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
If one or more tokens would be created under your control, twice that many of those tokens are created instead.

Koma's Coil

Evolution Sage

Landfall — Whenever a land you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Kraken

Voidslime

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

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Skullwinder

Deathtouch
When Skullwinder enters, return target card from your graveyard to your hand, then choose an opponent. That player returns a card from their graveyard to their hand.

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, Cosmos Serpent gains indestructible until end of turn.

Mimic Vat

Imprint — Whenever a nontoken creature dies, you may exile that card. If you do, return each other card exiled with Mimic Vat to its owner's graveyard.
{3}, {T}: Create a token that's a copy of a card exiled with Mimic Vat. It gains haste. Exile it at the beginning of the next end step.

Reef Worm

When Reef Worm dies, create a 3/3 blue Fish creature token with "When this creature dies, create a 6/6 blue Whale creature token with 'When this creature dies, create a 9/9 blue Kraken creature token.'"

Khalni Garden

Khalni Garden enters tapped.
When Khalni Garden enters, create a 0/1 green Plant creature token.
{T}: Add {G}.

Howling Golem

Whenever Howling Golem attacks or blocks, each player draws a card.

Trygon Predator

Flying
Whenever this creature deals combat damage to a player, you may destroy target artifact or enchantment that player controls.

Island

Mystic Confluence

Choose three. You may choose the same mode more than once.
• Counter target spell unless its controller pays {3}.
• Return target creature to its owner's hand.
• Draw a card.

Shipbreaker Kraken

{6}{U}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When Shipbreaker Kraken becomes monstrous, tap up to four target creatures. Those creatures don't untap during their controllers' untap steps for as long as you control Shipbreaker Kraken.

Theoretical Duplication

Whenever a nontoken creature an opponent controls enters this turn, create a token that's a copy of that creature.

Managorger Hydra

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

Sequence Engine

{X}, {T}: Exile target creature card with mana value X from a graveyard. Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it. Activate only as a sorcery.

Copy

(This token can be used to represent a token that's a copy of a permanent.)

Omnath, Locus of Mana

You don't lose unspent green mana as steps and phases end.
Omnath, Locus of Mana gets +1/+1 for each unspent green mana you have.

Doppelgang

For each of X target permanents, create X tokens that are copies of that permanent.

Forest

Junk Winder

Affinity for tokens (This spell costs {1} less to cast for each token you control.)
Whenever a token you control enters, tap target nonland permanent an opponent controls. It doesn't untap during its controller's next untap step.

Arcane Signet

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

Hunted Wumpus

When Hunted Wumpus enters, each other player may put a creature card from their hand onto the battlefield.

Tatyova, Benthic Druid

Landfall — Whenever a land you control enters, you gain 1 life and draw a card.

Karametra's Acolyte

{T}: Add an amount of {G} equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Ooze

Emissary Green

Whenever Emissary Green attacks, starting with you, each player votes for profit or security. You create a number of Treasure tokens equal to twice the number of profit votes. Put a number of +1/+1 counters on each creature you control equal to the number of security votes.

Biomathematician

When Biomathematician enters, create a 0/0 green and blue Fractal creature token. Put a +1/+1 counter on each Fractal you control.

Case of the Filched Falcon

When this Case enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
To solve — You control three or more artifacts. (If unsolved, solve at the beginning of your end step.)
Solved — {2}{U}, Sacrifice this Case: Put four +1/+1 counters on target noncreature artifact. It becomes a 0/0 Bird creature with flying in addition to its other types.