Tibalt, Cosmic Impostor

As Tibalt enters, you get an emblem with "You may play cards exiled with Tibalt, Cosmic Impostor, and you may spend mana as though it were mana of any color to cast those spells."
+2: Exile the top card of each player's library.
−3: Exile target artifact or creature.
−8: Exile all graveyards. Add {R}{R}{R}.

Getting

Valki, God of Lies

When Valki enters, each opponent reveals their hand. For each opponent, exile a creature card they revealed this way until Valki leaves the battlefield.
{X}: Choose a creature card exiled with Valki with mana value X. Valki becomes a copy of that card.

Valki, God of Lies // Tibalt, Cosmic Impostor

Have

Kalemne's Captain

Vigilance
{5}{W}{W}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Kalemne's Captain becomes monstrous, exile all artifacts and enchantments.

Island

Dark Impostor

{4}{B}{B}: Exile target creature and put a +1/+1 counter on Dark Impostor.
Dark Impostor has all activated abilities of all creature cards exiled with it.

Knacksaw Clique

Flying
{1}{U}, {Q}: Target opponent exiles the top card of their library. Until end of turn, you may play that card. ({Q} is the untap symbol.)

Linvala, Shield of Sea Gate

Flying
At the beginning of combat on your turn, if you have a full party, choose target nonland permanent an opponent controls. Until your next turn, it can't attack or block, and its activated abilities can't be activated.
Sacrifice Linvala: Choose hexproof or indestructible. Creatures you control gain that ability until end of turn.

Scavenging Ooze

{G}: Exile target card from a graveyard. If it was a creature card, put a +1/+1 counter on this creature and you gain 1 life.

Havengul Lich

{1}: You may cast target creature card in a graveyard this turn. When you cast it this turn, Havengul Lich gains all activated abilities of that card until end of turn.

Selvala, Explorer Returned

Parley — {T}: Each player reveals the top card of their library. For each nonland card revealed this way, add {G} and you gain 1 life. Then each player draws a card.

Biomancer's Familiar

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.
{T}: The next time target creature adapts this turn, it adapts as though it had no +1/+1 counters on it.

Devout Chaplain

{T}, Tap two untapped Humans you control: Exile target artifact or enchantment.

Spectral Sailor

Flash (You may cast this spell any time you could cast an instant.)
Flying
{3}{U}: Draw a card.

Ayli, Eternal Pilgrim

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
{1}, Sacrifice another creature: You gain life equal to the sacrificed creature's toughness.
{1}{W}{B}, Sacrifice another creature: Exile target nonland permanent. Activate only if you have at least 10 life more than your starting life total.

Plains

Mountain

Augusta, Dean of Order

Other tapped creatures you control get +1/+0.
Other untapped creatures you control get +0/+1.
Whenever you attack, untap each creature you control, then tap any number of creatures you control.

Plargg, Dean of Chaos

{T}, Discard a card: Draw a card.
{4}{R}, {T}: Reveal cards from the top of your library until you reveal a nonlegendary, nonland card with mana value 3 or less. You may cast that card without paying its mana cost. Put all revealed cards not cast this way on the bottom of your library in a random order.

Plargg, Dean of Chaos // Augusta, Dean of Order

Faeburrow Elder

Vigilance
Faeburrow Elder gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Cathar Commando

Flash (You may cast this spell any time you could cast an instant.)
{1}, Sacrifice this creature: Destroy target artifact or enchantment.

Wrenn and Realmbreaker

Lands you control have "{T}: Add one mana of any color."
+1: Up to one target land you control becomes a 3/3 Elemental creature with vigilance, hexproof, and haste until your next turn. It's still a land.
−2: Mill three cards. You may put a permanent card from among the milled cards into your hand.
−7: You get an emblem with "You may play lands and cast permanent spells from your graveyard."

Orthion, Hero of Lavabrink

{1}{R}, {T}: Create a token that's a copy of another target creature you control. It gains haste. Sacrifice it at the beginning of the next end step. Activate only as a sorcery.
{6}{R}{R}{R}, {T}: Create five tokens that are copies of another target creature you control. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.

Tazri, Stalwart Survivor

Each creature you control has "{T}: Add one mana of any of this creature's colors. Spend this mana only to activate an ability of a creature. Activate only if this creature has another activated ability."
{W}{U}{B}{R}{G}, {T}: Mill five cards. Put all creature cards with activated abilities that aren't mana abilities from among the milled cards into your hand.

Samut, Voice of Dissent

Flash
Double strike, vigilance, haste
Other creatures you control have haste.
{W}, {T}: Untap another target creature.

Yisan, the Wanderer Bard

{2}{G}, {T}, Put a verse counter on Yisan, the Wanderer Bard: Search your library for a creature card with mana value equal to the number of verse counters on Yisan, put it onto the battlefield, then shuffle.

Shalai, Voice of Plenty

Flying
You, planeswalkers you control, and other creatures you control have hexproof.
{4}{G}{G}: Put a +1/+1 counter on each creature you control.

Dynaheir, Invoker Adept

Haste
You may activate abilities of other creatures you control as though those creatures had haste.
{T}: When you next activate an ability that isn't a mana ability this turn by spending four or more mana to activate it, copy that ability. You may choose new targets for the copy.

Colossus of Akros

Defender, indestructible
{10}: Monstrosity 10. (If this creature isn't monstrous, put ten +1/+1 counters on it and it becomes monstrous.)
As long as Colossus of Akros is monstrous, it has trample and can attack as though it didn't have defender.

Cankerbloom

{1}, Sacrifice Cankerbloom: Choose one —
• Destroy target artifact.
• Destroy target enchantment.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Zirda, the Dawnwaker

Companion — Each permanent card in your starting deck has an activated ability. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Abilities you activate that aren't mana abilities cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.
{1}, {T}: Target creature can't block this turn.

Giltspire Avenger

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
{T}: Destroy target creature that dealt damage to you this turn.

Shamanic Revelation

Draw a card for each creature you control.
Ferocious — You gain 4 life for each creature you control with power 4 or greater.

Thousand-Year Elixir

You may activate abilities of creatures you control as though those creatures had haste.
{1}, {T}: Untap target creature.

Leyline of Abundance

If Leyline of Abundance is in your opening hand, you may begin the game with it on the battlefield.
Whenever you tap a creature for mana, add an additional {G}.
{6}{G}{G}: Put a +1/+1 counter on each creature you control.

Avatar of Woe

If there are ten or more creature cards total in all graveyards, this spell costs {6} less to cast.
Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{T}: Destroy target creature. It can't be regenerated.

Haywire Mite

When Haywire Mite dies, you gain 2 life.
{G}, Sacrifice Haywire Mite: Exile target noncreature artifact or noncreature enchantment.

Ioreth of the Healing House

{T}: Untap another target permanent.
{T}: Untap two other target legendary creatures.

Ethersworn Adjudicator

Flying
{1}{W}{B}, {T}: Destroy target creature or enchantment.
{2}{U}: Untap Ethersworn Adjudicator.

Sol Ring

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Ozolith, the Shattered Spire

If one or more +1/+1 counters would be put on an artifact or creature you control, that many plus one +1/+1 counters are put on it instead.
{1}{G}, {T}: Put a +1/+1 counter on target artifact or creature you control. Activate only as a sorcery.
Cycling {2} ({2}, Discard this card: Draw a card.)

Boromir, Warden of the Tower

Vigilance
Whenever an opponent casts a spell, if no mana was spent to cast it, counter that spell.
Sacrifice Boromir, Warden of the Tower: Creatures you control gain indestructible until end of turn. The Ring tempts you.

Agatha of the Vile Cauldron

Activated abilities of creatures you control cost {X} less to activate, where X is Agatha of the Vile Cauldron's power. This effect can't reduce the mana in that cost to less than one mana.
{4}{R}{G}: Other creatures you control get +1/+1 and gain trample and haste until end of turn.

Likeness Looter

Flying
{T}: Draw a card, then discard a card.
{X}: Likeness Looter becomes a copy of target creature card in your graveyard with mana value X, except it has flying and this ability. Activate only as a sorcery.

Faerie Formation

Flying
{3}{U}: Create a 1/1 blue Faerie creature token with flying. Draw a card.

Freed from the Real

Enchant creature
{U}: Tap enchanted creature.
{U}: Untap enchanted creature.

Experiment Kraj

Experiment Kraj has all activated abilities of each other creature with a +1/+1 counter on it.
{T}: Put a +1/+1 counter on target creature.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Gretchen Titchwillow

{2}{G}{U}: Draw a card. You may put a land card from your hand onto the battlefield.

Clay Golem

{6}, Roll a d8: Monstrosity X, where X is the result. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
Berserk — When Clay Golem becomes monstrous, destroy target permanent.

Walking Ballista

Walking Ballista enters with X +1/+1 counters on it.
{4}: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.

Fauna Shaman

{G}, {T}, Discard a creature card: Search your library for a creature card, reveal it, put it into your hand, then shuffle.

Chainer, Nightmare Adept

Discard a card: You may cast a creature spell from your graveyard this turn. Activate only once each turn.
Whenever a nontoken creature you control enters, if you didn't cast it from your hand, it gains haste until your next turn.

Order of Whiteclay

{1}{W}{W}, {Q}: Return target creature card with mana value 3 or less from your graveyard to the battlefield. ({Q} is the untap symbol.)

Goro-Goro, Disciple of Ryusei

{R}: Creatures you control gain haste until end of turn.
{3}{R}{R}: Create a 5/5 red Dragon Spirit creature token with flying. Activate only if you control an attacking modified creature. (Equipment, Auras you control, and counters are modifications.)

Omen Hawker

{T}: Add {C}{U}. Spend this mana only to activate abilities.

Vizier of Tumbling Sands

{T}: Untap another target permanent.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle Vizier of Tumbling Sands, untap target permanent.

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.

Agatha's Soul Cauldron

You may spend mana as though it were mana of any color to activate abilities of creatures you control.
Creatures you control with +1/+1 counters on them have all activated abilities of all creature cards exiled with Agatha's Soul Cauldron.
{T}: Exile target card from a graveyard. When a creature card is exiled this way, put a +1/+1 counter on target creature you control.

Shigeki, Jukai Visionary

{1}{G}, {T}, Return Shigeki, Jukai Visionary to its owner's hand: Reveal the top four cards of your library. You may put a land card from among them onto the battlefield tapped. Put the rest into your graveyard.
Channel — {X}{X}{G}{G}, Discard Shigeki: Return X target nonlegendary cards from your graveyard to your hand.

Kenrith, the Returned King

{R}: All creatures gain trample and haste until end of turn.
{1}{G}: Put a +1/+1 counter on target creature.
{2}{W}: Target player gains 5 life.
{3}{U}: Target player draws a card.
{4}{B}: Put target creature card from a graveyard onto the battlefield under its owner's control.

The Peregrine Dynamo

Haste
{1}, {T}: Copy target activated or triggered ability you control from another legendary source that's not a commander. You may choose new targets for the copy. (Mana abilities can't be targeted.)

Svella, Ice Shaper

{3}, {T}: Create a colorless snow artifact token named Icy Manalith with "{T}: Add one mana of any color."
{6}{R}{G}, {T}: Look at the top four cards of your library. You may cast a spell from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Kinnan, Bonder Prodigy

Whenever you tap a nonland permanent for mana, add one mana of any type that permanent produced.
{5}{G}{U}: Look at the top five cards of your library. You may put a non-Human creature card from among them onto the battlefield. Put the rest on the bottom of your library in a random order.

Swamp

Tyvar, Jubilant Brawler

You may activate abilities of creatures you control as though those creatures had haste.
+1: Untap up to one target creature.
−2: Mill three cards, then you may return a creature card with mana value 2 or less from your graveyard to the battlefield.

Zimone, Quandrix Prodigy

{1}, {T}: You may put a land card from your hand onto the battlefield tapped.
{4}, {T}: Draw a card. If you control eight or more lands, draw two cards instead.