Siphon Insight

Look at the top two cards of target opponent's library. Exile one of them face down and put the other on the bottom of that library. You may play the exiled card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.
Flashback {1}{U}{B}

The Council of Four

Whenever a player draws their second card during their turn, you draw a card.
Whenever a player casts their second spell during their turn, you create a 2/2 white Knight creature token.

Island

Cunning Rhetoric

Whenever an opponent attacks you and/or one or more planeswalkers you control, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast it.

Talisman of Hierarchy

{T}: Add {C}.
{T}: Add {W} or {B}. This artifact deals 1 damage to you.

Hallowed Fountain

({T}: Add {W} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Halo Forager

Flying
When this creature enters, you may pay {X}. When you do, you may cast target instant or sorcery card with mana value X from a graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Stolen Goods

Target opponent exiles cards from the top of their library until they exile a nonland card. Until end of turn, you may cast that card without paying its mana cost.

Godless Shrine

({T}: Add {W} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Lotho, Corrupt Shirriff

Whenever a player casts their second spell each turn, you lose 1 life and create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is this creature's power.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Maddening Cacophony

Kicker {3}{U}
Each opponent mills eight cards. If this spell was kicked, instead each opponent mills half their library, rounded up.

Propaganda

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

One Ring to Rule Them All

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — The Ring tempts you, then each player mills cards equal to your Ring-bearer's power.
II — Destroy all nonlegendary creatures.
III — Each opponent loses 1 life for each creature card in that player's graveyard.

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

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

Thought Scour

Target player mills two cards.
Draw a card.

Heliod, the Warped Eclipse

You may cast spells as though they had flash.
Spells you cast cost {1} less to cast for each card your opponents have drawn this turn.

Heliod, the Radiant Dawn

When Heliod enters, return target enchantment card that isn't a God from your graveyard to your hand.
{3}{U/P}: Transform Heliod. Activate only as a sorcery. ({U/P} can be paid with either {U} or 2 life.)

Heliod, the Radiant Dawn // Heliod, the Warped Eclipse

Talisman of Progress

{T}: Add {C}.
{T}: Add {W} or {U}. This artifact deals 1 damage to you.

Chaos Wand

{4}, {T}: Target opponent exiles cards from the top of their library until they exile an instant or sorcery card. You may cast that card without paying its mana cost. Then put the exiled cards that weren't cast this way on the bottom of that library in a random order.

Saruman of Many Colors

Ward—Discard an enchantment, instant, or sorcery card.
Whenever you cast your second spell each turn, each opponent mills two cards. When one or more cards are milled this way, exile target enchantment, instant, or sorcery card with equal or lesser mana value than that spell from an opponent's graveyard. Copy the exiled card. You may cast the copy without paying its mana cost.

Dimir Signet

Dramatic Reversal

Untap all nonland permanents you control.

Generous Gift

Destroy target permanent. Its controller creates a 3/3 green Elephant creature token.

Breach the Multiverse

Each player mills ten cards. For each player, choose a creature or planeswalker card in that player's graveyard. Put those cards onto the battlefield under your control. Then each creature you control becomes a Phyrexian in addition to its other types.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Command Tower

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

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Orzhov Signet

Lobelia Sackville-Baggins

Flash
Menace
When Lobelia enters, exile target creature card from an opponent's graveyard that was put there from the battlefield this turn, then create X Treasure tokens, where X is the exiled card's power.

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Blightwing Bandit

Flying, deathtouch
Whenever you cast your first spell during each opponent's turn, look at the top card of that player's library, then exile it face down. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast it.

Storm of Saruman

Ward {3}
Whenever you cast your second spell each turn, copy it, except the copy isn't legendary. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)

Polluted Delta

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Court of Cunning

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, any number of target players each mill two cards. If you're the monarch, each of those players mills ten cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)

Arcane Signet

Plains

Supreme Verdict

This spell can't be countered.
Destroy all creatures.

Dovin's Veto

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

Thran Dynamo

Despark

Exile target permanent with mana value 4 or greater.

Leyline of Anticipation

If this card is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Swamp

Dead Man's Chest

Enchant creature an opponent controls
When enchanted creature dies, exile cards equal to its power from the top of its owner's library. You may cast spells from among those cards for as long as they remain exiled, and mana of any type can be spent to cast them.

Austere Command

Choose two —
• Destroy all artifacts.
• Destroy all enchantments.
• Destroy all creatures with mana value 3 or less.
• Destroy all creatures with mana value 4 or greater.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Frantic Search

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

Saruman the White

Ward {2}
Whenever you cast your second spell each turn, amass Orcs 2. (Put two +1/+1 counters on an Army you control. It's also an Orc. If you don't control an Army, create a 0/0 black Orc Army creature token first.)

Farewell

Choose one or more —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all graveyards.

Wrath of God

Destroy all creatures. They can't be regenerated.

Watery Grave

({T}: Add {U} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Negate

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Exotic Orchard

Azorius Signet

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Marsh Flats

{T}, Pay 1 life, Sacrifice this land: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Misleading Signpost

Flash
When this artifact enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)
{T}: Add {U}.

Counterspell

Spell Pierce

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

Mesmeric Orb

Whenever a permanent becomes untapped, that permanent's controller mills a card.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Flooded Strand

{T}, Pay 1 life, Sacrifice this land: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Monk Class

(Gain the next level as a sorcery to add its ability.)
The second spell you cast each turn costs {1} less to cast.
{W}{U}: Level 2
When this Class becomes level 2, return up to one target nonland permanent to its owner's hand.
{1}{W}{U}: Level 3
At the beginning of your upkeep, exile the top card of your library. For as long as it remains exiled, it has "You may cast this card from exile as long as you've cast another spell this turn."

Sol Ring

Memory Plunder

You may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.

Snap

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

Ghostly Prison

Court of Locthwain

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, exile the top card of target opponent's library. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast it. If you're the monarch, until end of turn, you may cast a spell from among cards exiled with this enchantment without paying its mana cost.

Syr Konrad, the Grim

Whenever another creature dies, or a creature card is put into a graveyard from anywhere other than the battlefield, or a creature card leaves your graveyard, Syr Konrad deals 1 damage to each opponent.
{1}{B}: Each player mills a card. (They each put the top card of their library into their graveyard.)

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.