Overwhelming Encounter

Creatures you control gain vigilance and trample until end of turn. Roll a d20.
1—9 | Creatures you control get +2/+2 until end of turn.
10—19 | Put two +1/+1 counters on each creature you control.
20 | Put four +1/+1 counters on each creature you control.

Oceanus Dragon

Flying
When Oceanus Dragon enters, tap target creature an opponent controls. Goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Ganax, Astral Hunter

Flying
Whenever Ganax, Astral Hunter or another Dragon you control enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Choose a Background (You can have a Background as a second commander.)

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Carnelian Orb of Dragonkind

{T}: Add {R}. If that mana is spent on a Dragon creature spell, it gains haste until end of turn.

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

Navigation Orb

{2}, {T}, Sacrifice Navigation Orb: Search your library for up to two basic land cards and/or Gate cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Island

Chardalyn Dragon

Acolyte of Bahamut

Commander creatures you own have "The first Dragon spell you cast each turn costs {2} less to cast."

Molten Tributary

({T}: Add {U} or {R}.)
Molten Tributary enters tapped.

Lozhan, Dragons' Legacy

Flying
Whenever you cast an Adventure or Dragon spell, Lozhan, Dragons' Legacy deals damage equal to that spell's mana value to any target that isn't a commander.

Sand Augury

Scry 1, then draw a card. (Then exile this card. You may cast the creature later from exile.)

Young Blue Dragon

Young Blue Dragon // Sand Augury

Dragon Turtle

Flash
Drag Below — When Dragon Turtle enters, tap it and up to one target creature an opponent controls. They don't untap during their controllers' next untap steps.

Korlessa, Scale Singer

You may look at the top card of your library any time.
You may cast Dragon spells from the top of your library.

Ambitious Dragonborn

Ambitious Dragonborn enters with X +1/+1 counters on it, where X is the greatest power among creatures you control and creature cards in your graveyard.

Temple of the Dragon Queen

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

Dragon Hatchling

Flying
{R}: Dragon Hatchling gets +1/+0 until end of turn.

Dragon's Fire

As an additional cost to cast this spell, you may reveal a Dragon card from your hand or choose a Dragon you control.
Dragon's Fire deals 3 damage to target creature or planeswalker. If you revealed a Dragon card or chose a Dragon as you cast this spell, Dragon's Fire deals damage equal to the power of that card or creature instead.

Dragonborn Looter

{1}, {T}: Draw a card, then discard a card.

Zoological Study

Mill five cards, then return a creature card milled this way to your hand. (Then exile this card. You may cast the artifact later from exile.)

Monster Manual

{1}{G}, {T}: You may put a creature card from your hand onto the battlefield.

Monster Manual // Zoological Study

Draconic Lore

This spell costs {2} less to cast if you control a Dragon.
Draw three cards.

Earth Tremor

Earth Tremor deals damage to target creature or planeswalker equal to the number of lands you control.

Skanos Dragonheart

Whenever Skanos Dragonheart attacks, it gets +X/+X until end of turn, where X is the greatest power among other Dragons you control and Dragon cards in your graveyard.
Choose a Background (You can have a Background as a second commander.)

Sky Diamond

Bhaal's Invoker

Scorching Ray — {8}: Bhaal's Invoker deals 4 damage to each opponent.

Dragon's Approach

Dragon's Approach deals 3 damage to each opponent. You may exile Dragon's Approach and four cards named Dragon's Approach from your graveyard. If you do, search your library for a Dragon creature card, put it onto the battlefield, then shuffle.
A deck can have any number of cards named Dragon's Approach.

Silvanus's Invoker

Conjure Elemental — {8}: Untap target land you control. It becomes an 8/8 Elemental creature with trample and haste until end of turn. It's still a land.

Old Gnawbone

Flying
Whenever a creature you control deals combat damage to a player, create that many Treasure tokens.

Livaan, Cultist of Tiamat

Whenever you cast a noncreature spell, target creature gets +X/+0 until end of turn, where X is that spell's mana value.
Choose a Background (You can have a Background as a second commander.)

Dragonlord's Servant

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

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

Sword Coast Serpent can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Sea Gate

Sea Gate enters tapped.
As Sea Gate enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Decanter of Endless Water

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

Inferno of the Star Mounts

This spell can't be countered.
Flying, haste
{R}: Inferno of the Star Mounts gets +1/+0 until end of turn. When its power becomes 20 this way, it deals 20 damage to any target.

Red Dragon

Flying
Fire Breath — When Red Dragon enters, it deals 4 damage to each opponent.

Pseudodragon Familiar

Flying
{2}{U}: Target creature gains flying until end of turn.

Thrakkus the Butcher

Trample
Whenever Thrakkus the Butcher attacks, double the power of each Dragon you control until end of turn.

Arcane Signet

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

Forest

Mirror of Life Trapping

Whenever a creature enters, if it was cast, exile it, then return all other permanent cards exiled with Mirror of Life Trapping to the battlefield under their owners' control.

Dragon Whelp

Flying
{R}: Dragon Whelp gets +1/+0 until end of turn. If this ability has been activated four or more times this turn, sacrifice Dragon Whelp at the beginning of the next end step.

Majestic Genesis

Reveal the top X cards of your library, where X is the greatest mana value of a commander you own on the battlefield or in the command zone. You may put any number of permanent cards from among them onto the battlefield. Put the rest on the bottom of your library in a random order.

Wandering Troubadour

At the beginning of your end step, if you had a land enter the battlefield under your control this turn, venture into the dungeon. (Enter the first room or advance to the next room.)

Mountain

Crystal Grotto

When Crystal Grotto enters, scry 1.
{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Dragon Cultist

Commander creatures you own have "At the beginning of your end step, if a source you controlled dealt 5 or more damage this turn, create a 4/4 red Dragon creature token with flying."

Avenging Hunter

Trample
When Avenging Hunter enters, you take the initiative.

Galazeth Prismari

Flying
When Galazeth Prismari enters, create a Treasure token.
Artifacts you control have "{T}: Add one mana of any color. Spend this mana only to cast an instant or sorcery spell."

Lurking Green Dragon

Flying
Lurking Green Dragon can't attack unless defending player controls a creature with flying.

Forktail Sweep

Forktail Sweep deals 1 damage to each creature you don't control. (Then exile this card. You may cast the creature later from exile.)

Fang Dragon

Fang Dragon // Forktail Sweep

Stirring Bard

Defender
When Stirring Bard enters, you take the initiative.
Mantle of Inspiration — {T}: Target creature gains menace and haste until end of turn.

Patron of the Arts

When Patron of the Arts enters or dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Juvenile Mist Dragon

Flying
Confounding Clouds — When Juvenile Mist Dragon enters, for each opponent, tap up to one target creature that player controls. Each of those creatures doesn't untap during its controller's next untap step.

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.

Orb of Dragonkind

{1}, {T}: Add two mana in any combination of colors. Spend this mana only to cast Dragon spells or activate abilities of Dragons.
{R}, {T}, Sacrifice Orb of Dragonkind: Look at the top seven cards of your library. You may reveal a Dragon card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Scale Deflection

Put two +1/+1 counters on target creature and untap it. It gains hexproof until end of turn. (Then exile this card. You may cast the creature later from exile.)

Dread Linnorm

Dread Linnorm can't be blocked by creatures with power 3 or less.

Dread Linnorm // Scale Deflection

Feywild Visitor

Commander creatures you own have "Whenever one or more nontoken creatures you control deal combat damage to a player, you create a 1/1 blue Faerie Dragon creature token with flying."

Blue Dragon

Flying
Lightning Breath — When Blue Dragon enters, until your next turn, target creature an opponent controls gets -3/-0, up to one other target creature gets -2/-0, and up to one other target creature gets -1/-0.

Reckless Barbarian

Sacrifice Reckless Barbarian: Add {R}{R}.

Jaded Sell-Sword

When Jaded Sell-Sword enters, if mana from a Treasure was spent to cast it, it gains first strike and haste until end of turn.

Magda, Brazen Outlaw

Other Dwarves you control get +1/+0.
Whenever a Dwarf you control becomes tapped, create a Treasure token.
Sacrifice five Treasures: Search your library for an artifact or Dragon card, put that card onto the battlefield, then shuffle.

Garruk's Uprising

When this enchantment enters, if you control a creature with power 4 or greater, draw a card.
Creatures you control have trample. (Each of those creatures can deal excess combat damage to the player or planeswalker it's attacking.)
Whenever a creature you control with power 4 or greater enters, draw a card.

Lofty Denial

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

Evolving Wilds

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

Green Dragon

Flying
Poison Breath — When Green Dragon enters, until end of turn, whenever a creature an opponent controls is dealt damage, destroy it.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Lightning Shrieker

Flying, trample, haste
At the beginning of the end step, Lightning Shrieker's owner shuffles it into their library.

Jugan, the Rising Star

Flying
When Jugan, the Rising Star dies, you may distribute five +1/+1 counters among any number of target creatures.

Draconic Muralists

When Draconic Muralists dies, you may search your library for a Dragon card, reveal it, put it into your hand, then shuffle.