Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Three Blind Mice

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I — Create a 1/1 white Mouse creature token.
II, III — Create a token that's a copy of target token you control.
IV — Creatures you control get +1/+1 and gain vigilance until end of turn.

Avian Changeling

Changeling (This card is every creature type.)
Flying

Nomads en-Kor

{0}: The next 1 damage that would be dealt to Nomads en-Kor this turn is dealt to target creature you control instead.

Mouse Trapper

Flash
Valiant — Whenever Mouse Trapper becomes the target of a spell or ability you control for the first time each turn, tap target creature an opponent controls.

Nettle Guard

Valiant — Whenever Nettle Guard becomes the target of a spell or ability you control for the first time each turn, it gets +0/+2 until end of turn.
{1}, Sacrifice Nettle Guard: Destroy target artifact or enchantment.

Showdown of the Skalds

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Exile the top four cards of your library. Until the end of your next turn, you may play those cards.
II, III — Whenever you cast a spell this turn, put a +1/+1 counter on target creature you control.

Emberheart Challenger

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Valiant — Whenever Emberheart Challenger becomes the target of a spell or ability you control for the first time each turn, exile the top card of your library. Until end of turn, you may play that card.

Talisman of Conviction

{T}: Add {C}.
{T}: Add {R} or {W}. Talisman of Conviction deals 1 damage to you.

Fellwar Stone

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

Lupinflower Village

{T}: Add {C}.
{T}: Add {W}. Spend this mana only to cast a creature spell.
{1}{W}, {T}, Sacrifice Lupinflower Village: Look at the top six cards of your library. You may reveal a Bat, Bird, Mouse, or Rabbit card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Kindred Boon

As Kindred Boon enters, choose a creature type.
{1}{W}: Put a divinity counter on target creature you control of the chosen type.
Each creature you control with a divinity counter on it has indestructible.

Mirror Entity

Changeling (This card is every creature type.)
{X}: Until end of turn, creatures you control have base power and toughness X/X and gain all creature types.

Valley Questcaller

Whenever one or more other Rabbits, Bats, Birds, and/or Mice you control enter, scry 1.
Other Rabbits, Bats, Birds, and Mice you control get +1/+1.

Steelburr Champion

Offspring {1}{W} (You may pay an additional {1}{W} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Vigilance
Whenever an opponent casts a noncreature spell, put a +1/+1 counter on this creature.

Roughshod Duo

Trample
Whenever you expend 4, target creature you control gets +1/+1 and gains trample until end of turn. (You expend 4 as you spend your fourth total mana to cast spells during a turn.)

Spirit en-Kor

Flying
{0}: The next 1 damage that would be dealt to Spirit en-Kor this turn is dealt to target creature you control instead.

Whiskervale Forerunner

Valiant — Whenever Whiskervale Forerunner becomes the target of a spell or ability you control for the first time each turn, look at the top five cards of your library. You may reveal a creature card with mana value 3 or less from among them. You may put it onto the battlefield if it's your turn. If you don't put it onto the battlefield, put it into your hand. Put the rest on the bottom of your library in a random order.

Citadel Siege

As Citadel Siege enters, choose Khans or Dragons.
• Khans — At the beginning of combat on your turn, put two +1/+1 counters on target creature you control.
• Dragons — At the beginning of combat on each opponent's turn, tap target creature that player controls.

Manifold Mouse

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
At the beginning of combat on your turn, target Mouse you control gains your choice of double strike or trample until end of turn.

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on Bloodline Pretender.

Scholar of New Horizons

Scholar of New Horizons enters with a +1/+1 counter on it.
{T}, Remove a counter from a permanent you control: Search your library for a Plains card and reveal it. If an opponent controls more lands than you, you may put that card onto the battlefield tapped. If you don't put the card onto the battlefield, put it into your hand. Then shuffle.

Shared Animosity

Whenever a creature you control attacks, it gets +1/+0 until end of turn for each other attacking creature that shares a creature type with it.

Thistledown Players

Whenever Thistledown Players attacks, untap target nonland permanent.

Plains

Ranger of Eos

When Ranger of Eos enters, you may search your library for up to two creature cards with mana value 1 or less, reveal them, put them into your hand, then shuffle.

Blind Obedience

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Artifacts and creatures your opponents control enter tapped.

Raging Battle Mouse

The second spell you cast each turn costs {1} less to cast.
Celebration — At the beginning of combat on your turn, if two or more nonland permanents entered the battlefield under your control this turn, target creature you control gets +1/+1 until end of turn.

Canyon Jerboa

Landfall — Whenever a land you control enters, creatures you control get +1/+1 until end of turn.

Echoing Assault

Creature tokens you control have menace.
Whenever you attack a player, choose target nontoken creature that's attacking that player. Create a token that's a copy of that creature, except it's 1/1. The token enters tapped and attacking that player. Sacrifice it at the beginning of the next end step.

Charitable Levy

Noncreature spells cost {1} more to cast.
Whenever a player casts a noncreature spell, put a collection counter on Charitable Levy. Then if there are three or more collection counters on it, sacrifice it. If you do, draw a card, then you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Warrior en-Kor

{0}: The next 1 damage that would be dealt to Warrior en-Kor this turn is dealt to target creature you control instead.

Mountain

Paladin Class

(Gain the next level as a sorcery to add its ability.)
Spells your opponents cast during your turn cost {1} more to cast.
{2}{W}: Level 2
Creatures you control get +1/+1.
{4}{W}: Level 3
Whenever you attack, until end of turn, target attacking creature gets +1/+1 for each other attacking creature and gains double strike.

Valiant Changeling

This spell costs {1} less to cast for each creature type among creatures you control. This effect can't reduce the amount of mana this spell costs by more than {5}.
Changeling (This card is every creature type.)
Double strike

Thorn of Amethyst

Noncreature spells cost {1} more to cast.

Heartfire Hero

Valiant — Whenever Heartfire Hero becomes the target of a spell or ability you control for the first time each turn, put a +1/+1 counter on it.
When Heartfire Hero dies, it deals damage equal to its power to each opponent.

Seedglaive Mentor

Vigilance, haste
Valiant — Whenever Seedglaive Mentor becomes the target of a spell or ability you control for the first time each turn, put a +1/+1 counter on it.

Kismet

Artifacts, creatures, and lands your opponents control enter tapped.

Arcane Signet

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

The Irencrag

{T}: Add {C}.
Whenever a legendary creature you control enters, you may have The Irencrag become a legendary Equipment artifact named Everflame, Heroes' Legacy. If you do, it gains equip {3} and "Equipped creature gets +3/+3" and loses all other abilities.

Flowerfoot Swordmaster

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Valiant — Whenever this creature becomes the target of a spell or ability you control for the first time each turn, Mice you control get +1/+0 until end of turn.

Shaman en-Kor

{0}: The next 1 damage that would be dealt to Shaman en-Kor this turn is dealt to target creature you control instead.
{1}{W}: The next time a source of your choice would deal damage to target creature this turn, that damage is dealt to Shaman en-Kor instead.

Vryn Wingmare

Flying
Noncreature spells cost {1} more to cast.

Whiskerquill Scribe

Valiant — Whenever Whiskerquill Scribe becomes the target of a spell or ability you control for the first time each turn, you may discard a card. If you do, draw a card.

Rockface Village

{T}: Add {C}.
{T}: Add {R}. Spend this mana only to cast a creature spell.
{R}, {T}: Target Lizard, Mouse, Otter, or Raccoon you control gets +1/+0 and gains haste until end of turn. Activate only as a sorcery.

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Sol Ring

Puresteel Paladin

Whenever an Equipment you control enters, you may draw a card.
Metalcraft — Equipment you control have equip {0} as long as you control three or more artifacts.

Welcoming Vampire

Flying
Whenever one or more other creatures you control with power 2 or less enter, draw a card. This ability triggers only once each turn.

Loxodon Gatekeeper

Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on this creature.

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.

Mind Stone

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

Swords to Plowshares

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

Folk Hero

Commander creatures you own have "Whenever you cast a spell that shares a creature type with this creature, draw a card. This ability triggers only once each turn."

Outrider en-Kor

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
{0}: The next 1 damage that would be dealt to Outrider en-Kor this turn is dealt to target creature you control instead.

Odric, Lunarch Marshal

At the beginning of each combat, creatures you control gain first strike until end of turn if a creature you control has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, skulk, trample, and vigilance.

Mentor of the Meek

Whenever another creature you control with power 2 or less enters, you may pay {1}. If you do, draw a card.

Boros Signet

Thalia, Guardian of Thraben

First strike
Noncreature spells cost {1} more to cast.

Irregular Cohort

Changeling (This card is every creature type.)
When Irregular Cohort enters, create a 2/2 colorless Shapeshifter creature token with changeling.

Mabel, Heir to Cragflame

Other Mice you control get +1/+1.
When Mabel, Heir to Cragflame enters, create Cragflame, a legendary colorless Equipment artifact token with "Equipped creature gets +1/+1 and has vigilance, trample, and haste" and equip {2}.

Brambleguard Captain

At the beginning of combat on your turn, target creature you control gets +X/+0 until end of turn, where X is Brambleguard Captain's power.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Veteran Guardmouse

Valiant — Whenever Veteran Guardmouse becomes the target of a spell or ability you control for the first time each turn, it gets +1/+0 and gains first strike until end of turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Claim Jumper

Vigilance
When Claim Jumper enters, if an opponent controls more lands than you, you may search your library for a Plains card and put it onto the battlefield tapped. Then if an opponent controls more lands than you, repeat this process once. If you search your library this way, shuffle.