Demilich

This spell costs {U} less to cast for each instant and sorcery spell you've cast this turn.
Whenever Demilich attacks, exile up to one target instant or sorcery card from your graveyard. Copy it. You may cast the copy.
You may cast Demilich from your graveyard by exiling four instant and/or sorcery cards from your graveyard in addition to paying its other costs.

Web of Inertia

At the beginning of combat on each opponent's turn, that player may exile a card from their graveyard. If the player doesn't, creatures they control can't attack you this turn.

Sapphire Medallion

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

Aboshan's Desire

Enchant creature
Enchanted creature has flying.
Threshold — Enchanted creature has shroud as long as seven or more cards are in your graveyard. (It can't be the target of spells or abilities.)

Cephalid Scout

Flying
{2}{U}, Sacrifice a land: Draw a card.

Thwart

You may return three Islands you control to their owner's hand rather than pay this spell's mana cost.
Counter target spell.

Cephalid Snitch

Sacrifice Cephalid Snitch: Target creature loses protection from black until end of turn.

Levitation

Cephalid Sage

Threshold — As long as seven or more cards are in your graveyard, Cephalid Sage has "When Cephalid Sage enters the battlefield, draw three cards, then discard two cards."

Liquimetal Torque

{T}: Add {C}.
{T}: Target nonland permanent becomes an artifact in addition to its other types until end of turn.

Hylda's Crown of Winter

{1}, {T}: Tap target creature. This ability costs {1} less to activate during your turn.
{3}, Sacrifice Hylda's Crown of Winter: Draw a card for each tapped creature your opponents control.

Cephalid Pathmage

Cephalid Pathmage can't be blocked.
{T}, Sacrifice Cephalid Pathmage: Target creature can't be blocked this turn.

War Room

{T}: Add {C}.
{3}, {T}, Pay life equal to the number of colors in your commanders' color identity: Draw a card.

Cephalid Constable

Whenever Cephalid Constable deals combat damage to a player, return up to that many target permanents that player controls to their owner's hand.

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Scroll of Isildur

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Gain control of up to one target artifact for as long as you control Scroll of Isildur. The Ring tempts you.
II — Tap up to two target creatures. Put a stun counter on each of them.
III — Draw a card for each tapped creature target opponent controls.

Scrabbling Claws

{T}: Target player exiles a card from their graveyard.
{1}, Sacrifice Scrabbling Claws: Exile target card from a graveyard. Draw a card.

Voidmage Prodigy

{U}{U}, Sacrifice a Wizard: Counter target spell.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Cephalid Coliseum

{T}: Add {U}. Cephalid Coliseum deals 1 damage to you.
Threshold — {U}, {T}, Sacrifice Cephalid Coliseum: Target player draws three cards, then discards three cards. Activate only if seven or more cards are in your graveyard.

Cephalid Facetaker

Cephalid Facetaker can't be blocked.
At the beginning of combat on your turn, you may have Cephalid Facetaker become a copy of another target creature until end of turn, except it's 1/4 and has "This creature can't be blocked."

Blustersquall

Tap target creature you don't control.
Overload {3}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Back to Basics

Nonbasic lands don't untap during their controllers' untap steps.

Mass Manipulation

Gain control of X target creatures and/or planeswalkers.

Thought Vessel

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

Cephalid Inkshrouder

Discard a card: Cephalid Inkshrouder gains shroud until end of turn and can't be blocked this turn. (A creature with shroud can't be the target of spells or abilities.)

Island

Dismiss

Disciple of the Ring

{1}, Exile an instant or sorcery card from your graveyard: Choose one —
• Counter target noncreature spell unless its controller pays {2}.
• Disciple of the Ring gets +1/+1 until end of turn.
• Tap target creature.
• Untap target creature.

Betrayal

Enchant creature an opponent controls
Whenever enchanted creature becomes tapped, you draw a card.

Blue Sun's Twilight

Gain control of target creature with mana value X or less. If X is 5 or more, create a token that's a copy of that creature.

Borrowing 100,000 Arrows

Draw a card for each tapped creature target opponent controls.

Cephalid Aristocrat

Whenever Cephalid Aristocrat becomes the target of a spell or ability, mill two cards.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Riptide Replicator

As Riptide Replicator enters the battlefield, choose a color and a creature type.
Riptide Replicator enters the battlefield with X charge counters on it.
{4}, {T}: Create an X/X creature token of the chosen color and type, where X is the number of charge counters on Riptide Replicator.

Chamber of Manipulation

Enchant land
Enchanted land has "{T}, Discard a card: Gain control of target creature until end of turn."

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Negate

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters the battlefield, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.

Cephalid Vandal

At the beginning of your upkeep, put a shred counter on Cephalid Vandal. Then mill a card for each shred counter on Cephalid Vandal.

Castle Vantress

Castle Vantress enters the battlefield tapped unless you control an Island.
{T}: Add {U}.
{2}{U}{U}, {T}: Scry 2.

Cephalid Broker

{T}: Target player draws two cards, then discards two cards.

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Brainstorm

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

Theft of Dreams

Keep Watch

Sol Ring

Cephalid Illusionist

Whenever Cephalid Illusionist becomes the target of a spell or ability, mill three cards.
{2}{U}, {T}: Prevent all combat damage that would be dealt to and dealt by target creature you control this turn.

Pedantic Learning

Whenever a land card is put into your graveyard from your library, you may pay {1}. If you do, draw a card.

Think Tank

At the beginning of your upkeep, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Annul

Counter target artifact or enchantment spell.

Last Word

This spell can't be countered.
Counter target spell.

Sleep

Tap all creatures target player controls. Those creatures don't untap during that player's next untap step.

Reliquary Tower

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Callous Oppressor

You may choose not to untap Callous Oppressor during your untap step.
As Callous Oppressor enters the battlefield, an opponent chooses a creature type.
{T}: Gain control of target creature that isn't of the chosen type for as long as Callous Oppressor remains tapped.

Cephalid Looter

{T}: Target player draws a card, then discards a card.

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.

Aboshan, Cephalid Emperor

Tap an untapped Octopus you control: Tap target permanent.
{U}{U}{U}: Tap all creatures without flying.

Spell Swindle

Counter target spell. Create X Treasure tokens, where X is that spell's mana value. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Crab Umbra

Enchant creature
{2}{U}: Untap enchanted creature.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Harbinger of the Seas

Cephalid Retainer

{U}{U}: Tap target creature without flying.

Arcane Signet

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

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Admiral's Order

Raid — If you attacked this turn, you may pay {U} rather than pay this spell's mana cost.
Counter target spell.

Dissipate

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Thought Collapse

Counter target spell. Its controller mills three cards.

Counterspell

Memnarch

{1}{U}{U}: Target permanent becomes an artifact in addition to its other types. (This effect lasts indefinitely.)
{3}{U}: Gain control of target artifact. (This effect lasts indefinitely.)