Jon Irenicus, Shattered One

At the beginning of your end step, target opponent gains control of up to one target creature you control. Put two +1/+1 counters on it and tap it. It's goaded for the rest of the game and it gains "This creature can't be sacrificed." (It attacks each combat if able and attacks a player other than you if able.)
Whenever a creature you own but don't control attacks, you draw a card.

Manta Ray

This creature can't attack unless defending player controls an Island.
This creature can't be blocked except by blue creatures.
When you control no Islands, sacrifice this creature.

Arcane Signet

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

Go for the Throat

Dispel

Thalakos Deceiver

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever this creature attacks and isn't blocked, you may sacrifice it. If you do, gain control of target creature. (This effect lasts indefinitely.)

Telepathy

Your opponents play with their hands revealed.

Lurebound Scarecrow

As this creature enters, choose a color.
When you control no permanents of the chosen color, sacrifice this creature.

Countersquall

Counter target noncreature spell. Its controller loses 2 life.

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Counterspell

Aetherize

Return all attacking creatures to their owner's hand.

Island

Bog Serpent

This creature can't attack unless defending player controls a Swamp.
When you control no Swamps, sacrifice this creature.

Taniwha

Trample
Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)
At the beginning of your upkeep, all lands you control phase out. (They phase in before you untap during your next untap step.)

Island Fish Jasconius

This creature doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {U}{U}{U}. If you do, untap this creature.
This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.

Profane Tutor

Suspend 2—{1}{B} (Rather than cast this card from your hand, pay {1}{B} and exile it with two 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.)
Search your library for a card, put that card into your hand, then shuffle.

All Is Dust

Each player sacrifices all permanents they control that are one or more colors.

Frost Walker

When this creature becomes the target of a spell or ability, sacrifice it.

Sign in Blood

Target player draws two cards and loses 2 life.

Skeleton Ship

When you control no Islands, sacrifice Skeleton Ship.
{T}: Put a -1/-1 counter on target creature.

Dimir Machinations

Look at the top three cards of target player's library. Exile any number of those cards, then put the rest back in any order.
Transmute {1}{B}{B} ({1}{B}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Dimir Signet

Brainspoil

Destroy target creature that isn't enchanted. It can't be regenerated.
Transmute {1}{B}{B} ({1}{B}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Pirate Ship

This creature can't attack unless defending player controls an Island.
{T}: This creature deals 1 damage to any target.
When you control no Islands, sacrifice this creature.

Grid Monitor

Kukemssa Serpent

This creature can't attack unless defending player controls an Island.
{U}, Sacrifice an Island: Target land an opponent controls becomes an Island until end of turn.
When you control no Islands, sacrifice this creature.

Night's Whisper

Marjhan

This creature doesn't untap during your untap step.
{U}{U}, Sacrifice a creature: Untap this creature. Activate only during your upkeep.
This creature can't attack unless defending player controls an Island.
{U}{U}: This creature gets -1/-0 until end of turn and deals 1 damage to target attacking creature without flying.
When you control no Islands, sacrifice this creature.

Snap

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

Sea Serpent

This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.

Seasinger

When you control no Islands, sacrifice this creature.
You may choose not to untap this creature during your untap step.
{T}: Gain control of target creature whose controller controls an Island for as long as you control this creature and this creature remains tapped.

Fettergeist

Flying
At the beginning of your upkeep, sacrifice this creature unless you pay {1} for each other creature you control.

Propaganda

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

Rogue Class

(Gain the next level as a sorcery to add its ability.)
Whenever a creature you control deals combat damage to a player, exile the top card of that player's library face down. You may look at it for as long as it remains exiled.
{1}{U}{B}: Level 2
Creatures you control have menace.
{2}{U}{B}: Level 3
You may play cards exiled with Rogue Class, and you may spend mana as though it were mana of any color to cast those spells.

Exchange of Words

When this enchantment enters, choose two target creatures. For as long as this enchantment remains on the battlefield, exchange the text boxes of those creatures.

Strionic Resonator

{2}, {T}: Copy target triggered ability you control. You may choose new targets for the copy. (A triggered ability uses the words "when," "whenever," or "at.")

Necrotic Hex

Each player sacrifices six creatures of their choice. You create six tapped 2/2 black Zombie creature tokens.

Crawlspace

No more than two creatures can attack you each combat.

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Demonic Bargain

Exile the top thirteen cards of your library, then search your library for a card. Put that card into your hand, then shuffle.

Morkrut Necropod

Menace (This creature can't be blocked except by two or more creatures.)
Whenever this creature attacks or blocks, sacrifice another creature or land.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Decanter of Endless Water

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

Giant Shark

This creature can't attack unless defending player controls an Island.
Whenever this creature blocks or becomes blocked by a creature that has been dealt damage this turn, this creature gets +2/+0 and gains trample until end of turn.
When you control no Islands, sacrifice this creature.

Vodalian Knights

First strike
This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.
{U}: This creature gains flying until end of turn.

Sol Ring

Dandân

Swamp

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Steel Golem

Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Bronze Bombshell

When a player other than this creature's owner controls it, that player sacrifices it. If the player does, this creature deals 7 damage to the player.

Perplex

Counter target spell unless its controller discards their hand.
Transmute {1}{U}{B} ({1}{U}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Infernal Grasp

Destroy target creature. You lose 2 life.

Negate

Corrupted Conscience

Enchant creature
You control enchanted creature.
Enchanted creature has infect. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

The Trickster-God's Heist

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — You may exchange control of two target creatures.
II — You may exchange control of two target nonbasic, noncreature permanents that share a card type.
III — Target player loses 3 life and you gain 3 life.

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Heartless Summoning

Creature spells you cast cost {2} less to cast.
Creatures you control get -1/-1.

Xanathar, Guild Kingpin

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Clutch of the Undercity

Return target permanent to its owner's hand. Its controller loses 3 life.
Transmute {1}{U}{B} ({1}{U}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Fellwar Stone

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

Brackwater Elemental

When this creature attacks or blocks, sacrifice it at the beginning of the next end step.
Unearth {2}{U} ({2}{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.)