Waker of Waves

Creatures your opponents control get -1/-0.
{1}{U}, Discard this creature: Look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.

Mnemonic Nexus

Each player shuffles their graveyard into their library.

Ethereal Forager

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Flying
Whenever this creature attacks, you may return an instant or sorcery card exiled with this creature to its owner's hand.

Arcane Endeavor

Roll two d8 and choose one result. Draw cards equal to that result. Then you may cast an instant or sorcery spell with mana value less than or equal to the other result from your hand without paying its mana cost.

Mirage Mirror

{2}: This artifact becomes a copy of target artifact, creature, enchantment, or land until end of turn.

Witness Protection

Enchant creature
Enchanted creature loses all abilities and is a green and white Citizen creature with base power and toughness 1/1 named Legitimate Businessperson. (It loses all other colors, card types, creature types, and names.)

Stolen Identity

Create a token that's a copy of target artifact or creature.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Boomerang

Return target permanent to its owner's hand.

Pin to the Earth

Enchant creature
Enchanted creature gets -6/-0.

Dreamtide Whale

Vanishing 2 (This creature enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Whenever a player casts their second spell each turn, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Twisted Image

Switch target creature's power and toughness until end of turn.
Draw a card.

Island

Disruption Protocol

As an additional cost to cast this spell, tap an untapped artifact you control or pay {1}.
Counter target spell.

Reef Worm

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

Geistwave

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Narwhal

Serum Visions

Hesitation

When a player casts a spell, sacrifice this enchantment and counter that spell.

Steelfin Whale

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Whenever an artifact you control enters, untap this creature.

Get Out

Choose one —
• Counter target creature or enchantment spell.
• Return one or two target creatures and/or enchantments you own to your hand.

Portent

Look at the top three cards of target player's library, then put them back in any order. You may have that player shuffle.
Draw a card at the beginning of the next turn's upkeep.

Sol Ring

Aether Storm

Creature spells can't be cast.
Pay 4 life: Destroy Aether Storm. It can't be regenerated. Any player may activate this ability.

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Flow of Ideas

Amphibian Downpour

Flash
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies. Copies become tokens.)
Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1.

Star Whale

Flying, vigilance
Other creatures you control have ward {2}.
Suspend 6—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Contact Other Plane

Roll a d20.
1—9 | Draw two cards.
10—19 | Scry 2, then draw two cards.
20 | Scry 3, then draw three cards.

Orvar, the All-Form

Changeling
Whenever you cast an instant or sorcery spell, if it targets one or more other permanents you control, create a token that's a copy of one of those permanents.
When a spell or ability an opponent controls causes you to discard this card, create a token that's a copy of target permanent.

Shore Up

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

Brainsurge

Draw four cards, then put two cards from your hand on top of your library in any order.

Killer Whale

{U}: This creature gains flying until end of turn.

Cone of Cold

Roll a d20.
1—9 | Tap all creatures your opponents control.
10—19 | Tap all creatures your opponents control. Those creatures don't untap during their controllers' next untap steps.
20 | Tap all creatures your opponents control. Those creatures don't untap during their controllers' next untap steps. Until your next turn, creatures your opponents control enter tapped.

Negate

Pursued Whale

When this creature enters, each opponent creates a 1/1 red Pirate creature token with "This token can't block" and "Creatures you control attack each combat if able."
Spells your opponents cast that target this creature cost {3} more to cast.

Great Whale

When this creature enters, untap up to seven lands.

Long-Finned Skywhale

Flying
This creature can block only creatures with flying.

Planar Incision

Exile target artifact or creature, then return it to the battlefield under its owner's control with a +1/+1 counter on it.

Essence Scatter

Hulking Metamorph

Prototype {2}{U}{U} — 3/3 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
You may have this creature enter as a copy of an artifact or creature you control, except it's an artifact creature in addition to its other types, and its power and toughness are equal to this creature's power and toughness.

Lofty Denial

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Lookout's Dispersal

This spell costs {1} less to cast if you control a Pirate.
Counter target spell unless its controller pays {4}.

Dazzling Denial

Counter target spell unless its controller pays {2}. If you control a Bird, counter that spell unless its controller pays {4} instead.

Heirloom Blade

Equipped creature gets +3/+1.
Whenever equipped creature dies, you may reveal cards from the top of your library until you reveal a creature card that shares a creature type with it. Put that card into your hand and the rest on the bottom of your library in a random order.
Equip {1}

Neutralizing Blast

The Reality Chip

You may look at the top card of your library any time.
As long as The Reality Chip is attached to a creature, you may play lands and cast spells from the top of your library.
Reconfigure {2}{U} ({2}{U}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Aethertide Whale

Flying
When this creature enters, you get six {E} (energy counters).
Pay {E}{E}{E}{E}: Return this creature to its owner's hand.

Dynavolt Tower

Whenever you cast an instant or sorcery spell, you get {E}{E} (two energy counters).
{T}, Pay {E}{E}{E}{E}{E}: This artifact deals 3 damage to any target.

Chant of the Skifsang

Enchant creature
Enchanted creature gets -13/-0.

Enter the Enigma

Target creature can't be blocked this turn.
Draw a card.

Stasis Field

Enchant creature
Enchanted creature has base power and toughness 0/2, has defender, and loses all other abilities.

Thought Vessel

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

Phase Dolphin

Whenever this creature attacks, another target attacking creature can't be blocked this turn.

Illusionist's Stratagem

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.
Draw a card.

Colossal Whale

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever this creature attacks, you may exile target creature defending player controls until this creature leaves the battlefield. (That creature returns under its owner's control.)

Cackling Counterpart

Create a token that's a copy of target creature you control.
Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Aether Spike

Choose target spell. You get {E}{E} (two energy counters), then you may pay any amount of {E}. Counter that spell unless its controller pays {1} for each {E} paid this way.

Quasiduplicate

Create a token that's a copy of target creature you control.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Dream's Grip

Choose one —
• Tap target permanent.
• Untap target permanent.
Entwine {1} (Choose both if you pay the entwine cost.)

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Lagoon Breach

The owner of target attacking creature you don't control puts it on their choice of the top or bottom of their library.