The Jolly Balloon Man

Haste
{1}, {T}: Create a token that's a copy of another target creature you control, except it's a 1/1 red Balloon creature in addition to its other colors and types and it has flying and haste. Sacrifice it at the beginning of the next end step. Activate only as a sorcery.

Treasure Vault

{T}: Add {C}.
{X}{X}, {T}, Sacrifice Treasure Vault: Create X Treasure tokens.

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Seat of the Synod

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Grenzo, Havoc Raiser

Whenever a creature you control deals combat damage to a player, choose one —
• Goad target creature that player controls.
• Exile the top card of that player's library. Until end of turn, you may cast that card and you may spend mana as though it were mana of any color to cast that spell.

Rustvale Bridge

Rustvale Bridge enters tapped.
Indestructible
{T}: Add {R} or {W}.

Satya, Aetherflux Genius

Menace, haste
Whenever Satya, Aetherflux Genius attacks, create a tapped and attacking token that's a copy of up to one other target nontoken creature you control. You get {E}{E} (two energy counters). At the beginning of the next end step, sacrifice that token unless you pay an amount of {E} equal to its mana value.

Silverbluff Bridge

Silverbluff Bridge enters tapped.
Indestructible
{T}: Add {U} or {R}.

Talisman of Conviction

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

Frostboil Snarl

As Frostboil Snarl enters, you may reveal an Island or Mountain card from your hand. If you don't, Frostboil Snarl enters tapped.
{T}: Add {U} or {R}.

Island

Ancient Den

Glacial Fortress

Glacial Fortress enters tapped unless you control a Plains or an Island.
{T}: Add {W} or {U}.

Clifftop Retreat

Clifftop Retreat enters tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Plains

Whirler Virtuoso

When Whirler Virtuoso enters, you get {E}{E}{E} (three energy counters).
Pay {E}{E}{E}: Create a 1/1 colorless Thopter artifact creature token with flying.

HELIOS One

{T}: Add {C}.
{1}, {T}: You get {E} (an energy counter).
{3}, {T}, Pay X {E}, Sacrifice HELIOS One: Destroy target nonland permanent with mana value X. Activate only as a sorcery.

Exotic Orchard

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

Mountain

Furycalm Snarl

As Furycalm Snarl enters, you may reveal a Mountain or Plains card from your hand. If you don't, Furycalm Snarl enters tapped.
{T}: Add {R} or {W}.

Spire of Industry

{T}: Add {C}.
{T}, Pay 1 life: Add one mana of any color. Activate only if you control an artifact.

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.

Izzet Signet

Minas Tirith

Minas Tirith enters tapped unless you control a legendary creature.
{T}: Add {W}.
{1}{W}, {T}: Draw a card. Activate only if you attacked with two or more creatures this turn.

Brotherhood Scribe

Metalcraft — {T}: You get {E} (an energy counter). Activate only if you control three or more artifacts.
Whenever you get one or more {E} during your turn, creatures you control get +1/+1 until end of turn.

Command Tower

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

Glimmervoid

At the beginning of the end step, if you control no artifacts, sacrifice Glimmervoid.
{T}: Add one mana of any color.

Port Town

As Port Town enters, you may reveal a Plains or Island card from your hand. If you don't, Port Town enters tapped.
{T}: Add {W} or {U}.

Gonti's Aether Heart

Whenever Gonti's Aether Heart or another artifact you control enters, you get {E}{E} (two energy counters).
Pay eight {E}, Exile Gonti's Aether Heart: Take an extra turn after this one.

Palace Jailer

When Palace Jailer enters, you become the monarch.
When Palace Jailer enters, exile target creature an opponent controls until an opponent becomes the monarch.

Razortide Bridge

Razortide Bridge enters tapped.
Indestructible
{T}: Add {W} or {U}.

Fear of Missing Out

When Fear of Missing Out enters, discard a card, then draw a card.
Delirium — Whenever Fear of Missing Out attacks for the first time each turn, if there are four or more card types among cards in your graveyard, untap target creature. After this phase, there is an additional combat phase.

Buried Ruin

{T}: Add {C}.
{2}, {T}, Sacrifice Buried Ruin: Return target artifact card from your graveyard to your hand.

Aether Hub

When Aether Hub enters, you get {E} (an energy counter).
{T}: Add {C}.
{T}, Pay {E}: Add one mana of any color.

Guide of Souls

Whenever another creature you control enters, you gain 1 life and get {E} (an energy counter).
Whenever you attack, you may pay {E}{E}{E}. When you do, put two +1/+1 counters and a flying counter on target attacking creature. It becomes an Angel in addition to its other types.

Sulfur Falls

Sulfur Falls enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Imperial Recruiter

When Imperial Recruiter enters, search your library for a creature card with power 2 or less, reveal it, put it into your hand, then shuffle.