Saiba Cryptomancer

Flash
Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Hexproof

Helvault

{1}, {T}: Exile target creature you control.
{7}, {T}: Exile target creature you don't control.
When Helvault is put into a graveyard from the battlefield, return all cards exiled with it to the battlefield under their owners' control.

Peregrine Drake

Flying
When Peregrine Drake enters, untap up to five lands.

Oneirophage

Flying
Whenever you draw a card, put a +1/+1 counter on Oneirophage.

Identity Thief

Whenever Identity Thief attacks, you may exile another target nontoken creature. If you do, Identity Thief becomes a copy of that creature until end of turn. Return the exiled card to the battlefield under its owner's control at the beginning of the next end step.

Ovinize

Until end of turn, target creature loses all abilities and has base power and toughness 0/1.

Annul

Counter target artifact or enchantment spell.

Arcanis the Omnipotent

{T}: Draw three cards.
{2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Keep Safe

Counter target spell that targets a permanent you control.
Draw a card.

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

Sword Coast Serpent can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Kairi, the Swirling Sky

Flying, ward {3}
When Kairi, the Swirling Sky dies, choose one —
• Return any number of target nonland permanents with total mana value 6 or less to their owners' hands.
• Mill six cards, then return up to two instant and/or sorcery cards from your graveyard to your hand.

Thryx, the Sudden Storm

Flash
Flying
Spells you cast with mana value 5 or greater cost {1} less to cast and can't be countered.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Counterspell

Looter il-Kor

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever Looter il-Kor deals damage to an opponent, draw a card, then discard a card.

As Foretold

At the beginning of your upkeep, put a time counter on As Foretold.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on As Foretold.

Subtlety

Flash
Flying
When Subtlety enters, choose up to one target creature spell or planeswalker spell. Its owner puts it on the top or bottom of their library.
Evoke—Exile a blue card from your hand.

Sailors' Bane

This spell costs {1} less to cast for each card you own in exile and in your graveyard that's an instant card, a sorcery card, or a card that has an Adventure.
Ward {4} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)

Reject

Counter target creature or planeswalker spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Terisian Mindbreaker

Whenever Terisian Mindbreaker attacks, defending player mills half their library, rounded up.
Unearth {1}{U}{U}{U} ({1}{U}{U}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Sea-Dasher Octopus

Mutate {1}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flash
Whenever this creature deals combat damage to a player, draw a card.

Eldrazi Ravager

Annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent.)
Sacrifice two Eldrazi: Return Eldrazi Ravager from your graveyard to your hand.
Cycling {2} ({2}, Discard this card: Draw a card.)

Starlit Mantle

Flash
Enchant creature you control
When Starlit Mantle enters, enchanted creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Enchanted creature gets +1/+1.

Nadir Kraken

Whenever you draw a card, you may pay {1}. If you do, put a +1/+1 counter on Nadir Kraken and create a 1/1 blue Tentacle creature token.

Hauken's Insight

At the beginning of your upkeep, exile the top card of your library face down. You may look at that card for as long as it remains exiled.
Once during each of your turns, you may play a land or cast a spell from among the cards exiled with this permanent without paying its mana cost.

Jacob Hauken, Inspector

{T}: Draw a card, then exile a card from your hand face down. You may look at that card for as long as it remains exiled. You may pay {4}{U}{U}. If you do, transform Jacob Hauken, Inspector.

Jacob Hauken, Inspector // Hauken's Insight

Dungeon Geists

Flying
When Dungeon Geists enters, tap target creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Dungeon Geists.

Vision of the Unspeakable

Flying, trample
Vision of the Unspeakable gets +1/+1 for each card in your hand.

Behold the Unspeakable

(As this Saga enters and after your draw step, add a lore counter.)
I — Creatures you don't control get -2/-0 until your next turn.
II — If you have one or fewer cards in hand, draw four cards. Otherwise, scry 2, then draw two cards.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Behold the Unspeakable // Vision of the Unspeakable

Slinn Voda, the Rising Deep

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
When Slinn Voda, the Rising Deep enters, if it was kicked, return all creatures to their owners' hands except for Merfolk, Krakens, Leviathans, Octopuses, and Serpents.

In Bolas's Clutches

Enchant permanent
You control enchanted permanent.
Enchanted permanent is legendary.

Strategic Planning

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

Logic Knot

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Counter target spell unless its controller pays {X}.

Nulldrifter

When you cast this spell, draw two cards.
Flying
Annihilator 1 (Whenever this creature attacks, defending player sacrifices a permanent.)
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Didn't Say Please

Counter target spell. Its controller mills three cards.

Stunning Strike

Flash
Enchant creature
When Stunning Strike enters, tap enchanted creature and remove it from combat.
As long as enchanted creature isn't legendary, it doesn't untap during its controller's untap step.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Su-Chi Cave Guard

Vigilance
Ward {4} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)
When Su-Chi Cave Guard dies, add eight {C}. Until end of turn, you don't lose this mana as steps and phases end.

Island

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 Hulking Metamorph 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 Hulking Metamorph's power and toughness.

Blue Dragon

Flying
Lightning Breath — When Blue Dragon enters, until your next turn, target creature an opponent controls gets -3/-0, up to one other target creature gets -2/-0, and up to one other target creature gets -1/-0.

Lay Claim

Enchant permanent
You control enchanted permanent.
Cycling {2} ({2}, Discard this card: Draw a card.)

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Callaphe, Beloved of the Sea

Callaphe's power is equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
Creatures and enchantments you control have "Spells your opponents cast that target this permanent cost {1} more to cast."

String of Disappearances

Return target creature to its owner's hand. Then that creature's controller may pay {U}{U}. If the player does, they may copy this spell and may choose a new target for that copy.

Cavalier of Gales

Flying
When Cavalier of Gales enters, draw three cards, then put two cards from your hand on top of your library in any order.
When Cavalier of Gales dies, shuffle it into its owner's library, then scry 2.

Goggles of Night

Whenever equipped creature deals combat damage to a player, scry 1, then draw a card. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Essence Scatter

Depth Charge Colossus

Prototype {4}{U}{U} — 6/6 (You may cast this spell with different mana cost, color, and size. It keeps its abilities and types.)
Depth Charge Colossus doesn't untap during your untap step.
{3}: Untap Depth Charge Colossus.

Negate

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Thought Vessel

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

Triskaidekaphile

You have no maximum hand size.
At the beginning of your upkeep, if you have exactly thirteen cards in your hand, you win the game.
{3}{U}: Draw a card.

Neutralize

Counter target spell.
Cycling {2} ({2}, Discard this card: Draw a card.)

Pithing Needle

As Pithing Needle enters, choose a card name.
Activated abilities of sources with the chosen name can't be activated unless they're mana abilities.

Portent of Calamity

Reveal the top X cards of your library. For each card type, you may exile a card of that type from among them. Put the rest into your graveyard. You may cast a spell from among the exiled cards without paying its mana cost if you exiled four or more cards this way. Then put the rest of the exiled cards into your hand.

Thieving Otter

Whenever Thieving Otter deals damage to an opponent, draw a card.

Into the Story

This spell costs {3} less to cast if an opponent has seven or more cards in their graveyard.
Draw four cards.

Riddlemaster Sphinx

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Riddlemaster Sphinx enters, you may return target creature an opponent controls to its owner's hand.

One with the Multiverse

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library.
Once during each of your turns, you may cast a spell from your hand or the top of your library without paying its mana cost.

Meteor Golem

When Meteor Golem enters, destroy target nonland permanent an opponent controls.

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Stern Scolding

Counter target creature spell with power or toughness 2 or less.

Drownyard Lurker

Vigilance
When you cast or cycle Drownyard Lurker, create a 0/1 colorless Eldrazi Spawn creature token with "Sacrifice this creature: Add {C}."
Cycling {2}{U} ({2}{U}, Discard this card: Draw a card.)