Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Plains

Coil and Catch

Draw three cards, then discard a card. (Then shuffle this card into its owner's library.)

Marang River Regent

Flying
When this creature enters, return up to two other target nonland permanents to their owners' hands.

Marang River Regent // Coil and Catch

Call the Spirit Dragons

Dragons you control have indestructible.
At the beginning of your upkeep, for each color, put a +1/+1 counter on a Dragon you control of that color. If you put +1/+1 counters on five Dragons this way, you win the game.

Dragon

Claim Territory

Search your library for up to two basic Forest cards, reveal them, put one onto the battlefield tapped and the other into your hand, then shuffle. (Also shuffle this card.)

Maybe?

Bloomvine Regent

Flying
Whenever this creature or another Dragon you control enters, you gain 3 life.

Bloomvine Regent // Claim Territory

Utvara Hellkite

Flying
Whenever a Dragon you control attacks, create a 6/6 red Dragon creature token with flying.

Perilous Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Island, Mountain, or Plains card, put it onto the battlefield tapped, then shuffle.
Cycling {U}{R}{W} ({U}{R}{W}, Discard this card: Draw a card.)

Charring Bite

Charring Bite deals 5 damage to target creature without flying. (Then shuffle this card into its owner's library.)

Twinmaw Stormbrood

Flying
When this creature enters, you gain 5 life.

Twinmaw Stormbrood // Charring Bite

Boulderborn Dragon

Flying, vigilance
Whenever this creature attacks, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Maelstrom of the Spirit Dragon

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Dragon spell or an Omen spell.
{4}, {T}, Sacrifice this land: Search your library for a Dragon card, reveal it, put it into your hand, then shuffle.

Inevitable Defeat

This spell can't be countered.
Exile target nonland permanent. Its controller loses 3 life and you gain 3 life.

Magmatic Hellkite

Flying
When this creature enters, destroy target nonbasic land an opponent controls. Its controller searches their library for a basic land card, puts it onto the battlefield tapped with a stun counter on it, then shuffles. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Armament Dragon

Flying
When this creature enters, distribute three +1/+1 counters among one, two, or three target creatures you control.

Ramos, Dragon Engine

Flying
Whenever you cast a spell, put a +1/+1 counter on Ramos for each of that spell's colors.
Remove five +1/+1 counters from Ramos: Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Activate only once each turn.

Command Tower

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

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.")

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.

Roar of Endless Song

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Create a 5/5 green Elephant creature token.
III — Double the power and toughness of each creature you control until end of turn.

Rith, Liberated Primeval

Flying, ward {2}
Other Dragons you control have ward {2}.
At the beginning of your end step, if a creature or planeswalker an opponent controlled was dealt excess damage this turn, create a 4/4 red Dragon creature token with flying.

Canopy Gargantuan

Flying, ward {2}
At the beginning of your upkeep, put a number of +1/+1 counters on each other creature you control equal to that creature's toughness.

Petty Revenge

Destroy target creature with power 3 or less. (Then shuffle this card into its owner's library.)

Disruptive Stormbrood

Flying
When this creature enters, destroy up to one target artifact or enchantment.

Disruptive Stormbrood // Petty Revenge

Dispelling Exhale

As an additional cost to cast this spell, you may behold a Dragon. (You may choose a Dragon you control or reveal a Dragon card from your hand.)
Counter target spell unless its controller pays {2}. If a Dragon was beheld, counter that spell unless its controller pays {4} instead.

Ringing Strike Mastery

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.
Enchanted creature has "{5}: Untap this creature."

Spectral Denial

This spell costs {1} less to cast for each creature you control with power 4 or greater.
Counter target spell unless its controller pays {X}.

Spirit

Tranquil Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Forest, Plains, or Island card, put it onto the battlefield tapped, then shuffle.
Cycling {G}{W}{U} ({G}{W}{U}, Discard this card: Draw a card.)

The Prismatic Bridge

At the beginning of your upkeep, reveal cards from the top of your library until you reveal a creature or planeswalker card. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

Esika, God of the Tree

Vigilance
{T}: Add one mana of any color.
Other legendary creatures you control have vigilance and "{T}: Add one mana of any color."

Esika, God of the Tree // The Prismatic Bridge

Ureni of the Unwritten

Flying, trample
Whenever Ureni enters or attacks, look at the top eight cards of your library. You may put a Dragon creature card from among them onto the battlefield. Put the rest on the bottom of your library in a random order.

Hmmm...

Three Tree Mascot

Changeling (This card is every creature type.)
{1}: Add one mana of any color. Activate only once each turn.

Sol Ring

Elephant

Sphinx of the Second Sun

Flying
At the beginning of each of your postcombat main phases, there is an additional beginning phase after this phase. (The beginning phase includes the untap, upkeep, and draw steps.)

All-Out Assault

Creatures you control get +1/+1 and have deathtouch.
When this enchantment enters, if it's your main phase, there is an additional combat phase after this phase followed by an additional main phase. When you next attack this turn, untap each creature you control.

Arcane Signet

Thornwood Falls

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {G} or {U}.

Lithoform Engine

{2}, {T}: Copy target activated or triggered ability you control. You may choose new targets for the copy.
{3}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}, {T}: Copy target permanent spell you control. (The copy becomes a token.)

Mox Jasper

{T}: Add one mana of any color. Activate only if you control a Dragon.

Paradox Haze

Enchant player
At the beginning of enchanted player's first upkeep each turn, that player gets an additional upkeep step after this step.

Copy

(This token can be used to represent a token that's a copy of a permanent.)

Perennation

Return target permanent card from your graveyard to the battlefield with a hexproof counter and an indestructible counter on it.

Sonic Shrieker

Flying
When this creature enters, it deals 2 damage to any target and you gain 2 life. If a player is dealt damage this way, they discard a card.

Chilling Screech

Counter target spell with mana value 2 or less. (Then shuffle this card into its owner's library.)

Runescale Stormbrood

Flying
Whenever you cast a noncreature spell or a Dragon spell, this creature gets +2/+0 until end of turn.

Runescale Stormbrood // Chilling Screech

Bountiful Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Forest, Island, or Mountain card, put it onto the battlefield tapped, then shuffle.
Cycling {G}{U}{R} ({G}{U}{R}, Discard this card: Draw a card.)

Betor, Kin to All

Flying
At the beginning of your end step, if creatures you control have total toughness 10 or greater, draw a card. Then if creatures you control have total toughness 20 or greater, untap each creature you control. Then if creatures you control have total toughness 40 or greater, each opponent loses half their life, rounded up.

Frontier Bivouac

This land enters tapped.
{T}: Add {G}, {U}, or {R}.

Scion of Draco

Domain — This spell costs {2} less to cast for each basic land type among lands you control.
Flying
Each creature you control has vigilance if it's white, hexproof if it's blue, lifelink if it's black, first strike if it's red, and trample if it's green.

Temur Battlecrier

During your turn, spells you cast cost {1} less to cast for each creature you control with power 4 or greater.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Karakyk Guardian

Flying, vigilance, trample
This creature has hexproof if it hasn't dealt damage yet. (It can't be the target of spells or abilities your opponents control.)

Minion of the Mighty

Menace
Pack tactics — Whenever this creature attacks, if you attacked with creatures with total power 6 or greater this combat, you may put a Dragon creature card from your hand onto the battlefield tapped and attacking.

Foreboding Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Swamp, Forest, or Island card, put it onto the battlefield tapped, then shuffle.
Cycling {B}{G}{U} ({B}{G}{U}, Discard this card: Draw a card.)

Opulent Palace

This land enters tapped.
{T}: Add {B}, {G}, or {U}.

Dragonclaw Strike

Double the power and toughness of target creature you control until end of turn. Then it fights up to one target creature an opponent controls. (Each deals damage equal to its power to the other.)

Swiftwater Cliffs

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {R}.

Cascading Cataracts

Indestructible
{T}: Add {C}.
{5}, {T}: Add five mana in any combination of colors.

Dismal Backwater

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {B}.

Jeskai Shrinekeeper

Flying, haste
Whenever this creature deals combat damage to a player, you gain 1 life and draw a card.

Repulsive Mutation

Put X +1/+1 counters on target creature you control. Then counter up to one target spell unless its controller pays mana equal to the greatest power among creatures you control.

Dragon's Hoard

Whenever a Dragon you control enters, put a gold counter on this artifact.
{T}, Remove a gold counter from this artifact: Draw a card.
{T}: Add one mana of any color.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Warden of the Grove

At the beginning of your end step, put a +1/+1 counter on this creature.
Whenever another nontoken creature you control enters, it endures X, where X is the number of counters on this creature. (Put X +1/+1 counters on the creature that entered or create an X/X white Spirit creature token.)

Dynamic Soar

Put three +1/+1 counters on target creature you control. (Then shuffle this card into its owner's library.)

Whirlwing Stormbrood

Flash
Flying
You may cast sorcery spells and Dragon spells as though they had flash.

Whirlwing Stormbrood // Dynamic Soar

Miirym, Sentinel Wyrm

Flying, ward {2}
Whenever another nontoken Dragon you control enters, create a token that's a copy of it, except the token isn't legendary.

Temple of the Dragon Queen

As this land enters, you may reveal a Dragon card from your hand. This land enters tapped unless you revealed a Dragon card this way or you control a Dragon.
As this land enters, choose a color.
{T}: Add one mana of the chosen color.

Swamp

Shapesharer

Changeling (This card is every creature type.)
{2}{U}: Target Shapeshifter becomes a copy of target creature until your next turn.

Secluded Courtyard

As this land enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type or activate an ability of a creature source of the chosen type.

Roost Seek

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Also shuffle this card.)

Sagu Wildling

Flying
When this creature enters, you gain 3 life.

Sagu Wildling // Roost Seek

Mountain

Mistrise Village

This land enters tapped unless you control a Mountain or a Forest.
{T}: Add {U}.
{U}, {T}: The next spell you cast this turn can't be countered.

Remnant of the Rising Star

Flying
Whenever another creature you control enters, you may pay {X}. When you do, put X +1/+1 counters on that creature.
As long as you control five or more modified creatures, this creature gets +5/+5 and has trample. (Equipment, Auras you control, and counters are modifications.)

Jugan Defends the Temple

(As this Saga enters and after your draw step, add a lore counter.)
I — Create a 1/1 green Human Monk creature token with "{T}: Add {G}."
II — Put a +1/+1 counter on each of up to two target creatures.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Jugan Defends the Temple // Remnant of the Rising Star

Lie in Wait

Return target creature card from your graveyard to your hand. Lie in Wait deals damage equal to that card's power to target creature.

Absorb Essence

Target creature gets +2/+2 and gains lifelink and hexproof until end of turn. (Then shuffle this card into its owner's library.)

Purging Stormbrood

Flying
Ward—Pay 2 life.
When this creature enters, remove all counters from up to one target creature.

Purging Stormbrood // Absorb Essence

Sandsteppe Citadel

This land enters tapped.
{T}: Add {W}, {B}, or {G}.

Tranquil Cove

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {U}.

Alesha's Legacy

Target creature you control gains deathtouch and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Island

Fabled Passage

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Rugged Highlands

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {R} or {G}.

Turn Aside

Counter target spell that targets a permanent you control.

Ureni, the Song Unending

Flying, protection from white and from black
When Ureni enters, it deals X damage divided as you choose among any number of target creatures and/or planeswalkers your opponents control, where X is the number of lands you control.

Mystic Monastery

This land enters tapped.
{T}: Add {U}, {R}, or {W}.

Voice of Victory

Mobilize 2 (Whenever this creature attacks, create two tapped and attacking 1/1 red Warrior creature tokens. Sacrifice them at the beginning of the next end step.)
Your opponents can't cast spells during your turn.

Dragonstorm Globe

Each Dragon you control enters with an additional +1/+1 counter on it.
{T}: Add one mana of any color.

Beledros Witherbloom

Flying
At the beginning of each upkeep, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
Pay 10 life: Untap all lands you control. Activate only once each turn.

Encroaching Dragonstorm

When this enchantment enters, search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.
When a Dragon you control enters, return this enchantment to its owner's hand.

Nomad Outpost

This land enters tapped.
{T}: Add {R}, {W}, or {B}.