Counterspell

Mystery Key

When equipped creature deals combat damage to a player, sacrifice Mystery Key. If you do, draw three cards.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Looming Altisaur

Cathar's Shield

Equipped creature gets +0/+3 and has vigilance.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

The Council of Four

Whenever a player draws their second card during their turn, you draw a card.
Whenever a player casts their second spell during their turn, you create a 2/2 white Knight creature token.

Birthday Escape

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.

Goliath Paladin

Vigilance
When Goliath Paladin enters, you take the initiative.

Dragon's Eye Savants

Morph—Reveal a blue card in your hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Dragon's Eye Savants is turned face up, look at target opponent's hand.

Giant Ox

Giant Ox crews Vehicles using its toughness rather than its power.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Lagonna-Band Trailblazer

Heroic — Whenever you cast a spell that targets Lagonna-Band Trailblazer, put a +1/+1 counter on Lagonna-Band Trailblazer.

Loran's Escape

Target artifact or creature gains hexproof and indestructible until end of turn. Scry 1.

Kraken Hatchling

Sword Coast Sailor

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, this creature can't be blocked this turn."

Charix, the Raging Isle

Spells your opponents cast that target Charix, the Raging Isle cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.

Refuse to Yield

Target creature gets +2/+7 until end of turn. Untap it.

High Alert

Each creature you control assigns combat damage equal to its toughness rather than its power.
Creatures you control can attack as though they didn't have defender.
{2}{W}{U}: Untap target 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.

Sidisi's Faithful

Exploit (When this creature enters, you may sacrifice a creature.)
When Sidisi's Faithful exploits a creature, return target creature to its owner's hand.

Armored Armadillo

Ward {1} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)
{3}{W}: Armored Armadillo gets +X/+0 until end of turn, where X is its toughness.

Hero's Resolve

Enchant creature
Enchanted creature gets +1/+5.

Secret Rendezvous

You and target opponent each draw three cards.

Accorder's Shield

Equipped creature gets +0/+3 and has vigilance. (Attacking doesn't cause it to tap.)
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Trailblazer's Torch

When Trailblazer's Torch enters, you take the initiative.
Whenever equipped creature becomes blocked, it deals 2 damage to each creature blocking it.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Yoked Ox

Slagwurm Armor

Equipped creature gets +0/+6.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery. This card enters unattached and stays on the battlefield if the creature leaves.)

Skeleton Key

Equipped creature has skulk. (It can't be blocked by creatures with greater power.)
Whenever equipped creature deals combat damage to a player, you may draw a card. If you do, discard a card.
Equip {2}

Brave the Sands

Creatures you control have vigilance.
Each creature you control can block an additional creature each combat.

Nyx-Fleece Ram

At the beginning of your upkeep, you gain 1 life.

Aegis Turtle

Aetherize

Return all attacking creatures to their owner's hand.

Cut a Deal

Each opponent draws a card, then you draw a card for each opponent who drew a card this way.

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Tetsuko Umezawa, Fugitive

Creatures you control with power or toughness 1 or less can't be blocked.

Chosen by Heliod

Enchant creature
When Chosen by Heliod enters, draw a card.
Enchanted creature gets +0/+2.

No More Lies

Counter target spell unless its controller pays {3}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Ancient Crab

Generous Gift

Destroy target permanent. Its controller creates a 3/3 green Elephant creature token.

Feywild Caretaker

When Feywild Caretaker enters, you take the initiative.
At the beginning of your end step, if you have the initiative, create a 1/1 blue Faerie Dragon creature token with flying.

Seasoned Dungeoneer

When Seasoned Dungeoneer enters, you take the initiative.
Whenever you attack, target attacking Cleric, Rogue, Warrior, or Wizard gains protection from creatures until end of turn. It explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)

Slaughter the Strong

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Sejiri Glacier

Sejiri Glacier enters tapped.
{T}: Add {W}.

Sejiri Shelter

Target creature you control gains protection from the color of your choice until end of turn.

Sejiri Shelter // Sejiri Glacier

Solidarity

Creatures you control get +0/+5 until end of turn.

Ensouled Scimitar

{3}: Ensouled Scimitar becomes a 1/5 Spirit artifact creature with flying until end of turn. (Equipment that's a creature can't equip a creature.)
Equipped creature gets +1/+5.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Surge Mare

Surge Mare can't be blocked by green creatures.
Whenever Surge Mare deals damage to an opponent, you may draw a card. If you do, discard a card.
{1}{U}: Surge Mare gets +2/-2 until end of turn.

Ornithopter of Paradise

Thought Vessel

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

Holy Armor

Enchant creature
Enchanted creature gets +0/+2.
{W}: Enchanted creature gets +0/+1 until end of turn.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

The Battle of Bywater

Destroy all creatures with power 3 or greater. Then create a Food token for each creature you control. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

Aarakocra Sneak

Flying
When Aarakocra Sneak enters, you take the initiative.

Expel the Interlopers

Choose a number between 0 and 10. Destroy all creatures with power greater than or equal to the chosen number.

Dawn

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Return all creature cards with power 2 or less from your graveyard to your hand.

Dusk

Destroy all creatures with power 3 or greater.

Dusk // Dawn

Sarevok's Tome

When Sarevok's Tome enters, you take the initiative.
{T}: Add {C}. If you have the initiative, add {C}{C} instead.
{3}, {T}: Exile cards from the top of your library until you exile a nonland card. You may cast that card without paying its mana cost. Activate only if you've completed a dungeon.

Crashing Drawbridge

Defender
{T}: Creatures you control gain haste until end of turn.

Writ of Passage

Enchant creature
Whenever enchanted creature attacks, if its power is 2 or less, it can't be blocked this turn.
Forecast — {1}{U}, Reveal Writ of Passage from your hand: Target creature with power 2 or less can't be blocked this turn. (Activate only during your upkeep and only once each turn.)

Essence of Antiquity

Disguise {2}{W} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)
When Essence of Antiquity is turned face up, creatures you control gain hexproof until end of turn. Untap them.

Negate

Aegis of the Heavens

Target creature gets +1/+7 until end of turn.

Oathsworn Giant

Vigilance
Other creatures you control get +0/+2 and have vigilance.

Rasaad yn Bashir

Each creature you control assigns combat damage equal to its toughness rather than its power.
Whenever Rasaad yn Bashir attacks, if you have the initiative, double the toughness of each creature you control until end of turn.
Choose a Background (You can have a Background as a second commander.)

Eland Umbra

Enchant creature
Enchanted creature gets +0/+4.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Wall of Frost

Defender
Whenever Wall of Frost blocks a creature, that creature doesn't untap during its controller's next untap step.

Cephalid Facetaker

Cephalid Facetaker can't be blocked.
At the beginning of combat on your turn, you may have Cephalid Facetaker become a copy of another target creature until end of turn, except it's 1/4 and has "This creature can't be blocked."

Bar the Door

Creatures you control get +0/+4 until end of turn.

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.

Hard Evidence

Create a 0/3 blue Crab creature token.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Arcane Signet

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

Gold-Forged Thopteryx

Flying, lifelink
Each legendary permanent you control has ward {2}. (Whenever it becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Flaming Fist

Commander creatures you own have "Whenever this creature attacks, it gains double strike until end of turn."

Iron Will

Target creature gets +0/+4 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

God-Pharaoh's Faithful

Whenever you cast a blue, black, or red spell, you gain 1 life.

Disenchant

Shell Shield

Kicker {1} (You may pay an additional {1} as you cast this spell.)
Target creature you control gets +0/+3 until end of turn. If this spell was kicked, that creature also gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Stroke of Midnight

Destroy target nonland permanent. Its controller creates a 1/1 white Human creature token.

Soulless Jailer

Permanent cards in graveyards can't enter the battlefield.
Players can't cast noncreature spells from graveyards or exile.

Belbe's Armor

{X}, {T}: Target creature gets -X/+X until end of turn.

Zetalpa, Primal Dawn

Flying, double strike, vigilance, trample, indestructible

Mizzium Skin

Target creature you control gets +0/+1 and gains hexproof until end of turn.
Overload {1}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Fell the Mighty

Destroy all creatures with power greater than target creature's power.

Conclave's Blessing

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Enchant creature
Enchanted creature gets +0/+2 for each other creature you control.

Blacksmith's Skill

Target permanent gains hexproof and indestructible until end of turn. If it's an artifact creature, it gets +2/+2 until end of turn.

Tasseled Dromedary

Stoneskin

Flash
Enchant creature
Enchanted creature gets +0/+10.

Assemble the Players

You may look at the top card of your library any time.
Once each turn, you may cast a creature spell with power 2 or less from the top of your library.

Crystacean

Flash (You may cast this spell any time you could cast an instant.)

Wall of Denial

Defender, flying
Shroud (This creature can't be the target of spells or abilities.)

Tomb of Horrors Adventurer

When Tomb of Horrors Adventurer enters, you take the initiative.
Whenever you cast your second spell each turn, copy it. If you've completed a dungeon, copy that spell twice instead. You may choose new targets for the copies. (A copy of a permanent spell becomes a token.)

Sol Ring

Winged Boots

Equipped creature has flying and ward {4}. (Whenever equipped creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)
Equip {1}

Baldin, Century Herdmaster

As long as it's your turn, each creature assigns combat damage equal to its toughness rather than its power.
Whenever Baldin, Century Herdmaster attacks, up to one hundred target creatures each get +0/+X until end of turn, where X is the number of cards in your hand.