Unbreakable Formation

Creatures you control gain indestructible until end of turn.
Addendum — If you cast this spell during your main phase, put a +1/+1 counter on each of those creatures and they gain vigilance until end of turn.

Stoneforge Masterwork

Equipped creature gets +1/+1 for each other creature you control that shares a creature type with it.
Equip {2}

Brave the Sands

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

Fellwar Stone

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

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Shattered Landscape

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

Firemane Commando

Flying
Whenever you attack with two or more creatures, draw a card.
Whenever another player attacks with two or more creatures, they draw a card if none of those creatures attacked you.

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Aerial Surveyor

Flying
Whenever Aerial Surveyor attacks, if defending player controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.
Crew 2

General's Kabuto

Equipped creature has shroud. (It can't be the target of spells or abilities.)
Prevent all combat damage that would be dealt to equipped creature.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Read the Bones

Scry 2, then draw two cards. You lose 2 life. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Stroke of Midnight

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

Nezumi Bladeblesser

Nezumi Bladeblesser has deathtouch as long as you control an artifact.
Nezumi Bladeblesser has menace as long as you control an enchantment. (It can't be blocked except by two or more creatures.)

Sol Ring

You Are Already Dead

Destroy target creature that was dealt damage this turn.
Draw a card.

Bloodstained Mire

{T}, Pay 1 life, Sacrifice Bloodstained Mire: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Captain Lannery Storm

Haste
Whenever Captain Lannery Storm attacks, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever you sacrifice a Treasure, Captain Lannery Storm gets +1/+0 until end of turn.

Peerless Samurai

Menace (This creature can't be blocked except by two or more creatures.)
Whenever a Samurai or Warrior you control attacks alone, the next spell you cast this turn costs {1} less to cast.

Isshin, Two Heavens as One

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

Sokenzan Spellblade

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
{1}{R}: Sokenzan Spellblade gets +X/+0 until end of turn, where X is the number of cards in your hand.

Grand Melee

All creatures attack each combat if able.
All creatures block each combat if able.

Assault Suit

Equipped creature gets +2/+2, has haste, can't attack you or planeswalkers you control, and can't be sacrificed.
At the beginning of each opponent's upkeep, you may have that player gain control of equipped creature until end of turn. If you do, untap it.
Equip {3}

Mountain

Ronin Cavekeeper

Bushido 2 (Whenever this creature blocks or becomes blocked, it gets +2/+2 until end of turn.)

Nomad Outpost

Nomad Outpost enters tapped.
{T}: Add {R}, {W}, or {B}.

Plains

Acererak the Archlich

When Acererak the Archlich enters, if you haven't completed Tomb of Annihilation, return Acererak the Archlich to its owner's hand and venture into the dungeon.
Whenever Acererak the Archlich attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature of their choice.

Etali, Primal Storm

Whenever Etali attacks, exile the top card of each player's library, then you may cast any number of spells from among those cards without paying their mana costs.

Audacious Thief

Whenever Audacious Thief attacks, you draw a card and you lose 1 life.

Raiyuu, Storm's Edge

First strike
Whenever a Samurai or Warrior you control attacks alone, untap it. If it's the first combat phase of the turn, there is an additional combat phase after this phase.

Orzhov Signet

Angelic Exaltation

Whenever a creature you control attacks alone, it gets +X/+X until end of turn, where X is the number of creatures you control.

Capital Punishment

Council's dilemma — Starting with you, each player votes for death or taxes. Each opponent sacrifices a creature of their choice for each death vote and discards a card for each taxes vote.

Devoted Retainer

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)

Konda's Hatamoto

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
As long as you control a legendary Samurai, Konda's Hatamoto gets +1/+2 and has vigilance. (Attacking doesn't cause this creature to tap.)

Numai Outcast

Bushido 2 (Whenever this creature blocks or becomes blocked, it gets +2/+2 until end of turn.)
{B}, Pay 5 life: Regenerate Numai Outcast.

Prowler's Helm

Equipped creature can't be blocked except by Walls.
Equip {2}

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Infiltration Lens

Whenever equipped creature becomes blocked by a creature, you may draw two cards.
Equip {1}

Peregrine Mask

Equipped creature has defender, flying, and first strike.
Equip {2}

Sigiled Sword of Valeron

Equipped creature gets +2/+0, has vigilance, and is a Knight in addition to its other types.
Whenever equipped creature attacks, create a 2/2 white Knight creature token with vigilance that's attacking.
Equip {3}

Arcane Signet

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

Laelia, the Blade Reforged

Haste
Whenever Laelia, the Blade Reforged attacks, exile the top card of your library. You may play that card this turn.
Whenever one or more cards are put into exile from your library and/or your graveyard, put a +1/+1 counter on Laelia.

Shared Animosity

Whenever a creature you control attacks, it gets +1/+0 until end of turn for each other attacking creature that shares a creature type with it.

Selfless Samurai

Whenever a Samurai or Warrior you control attacks alone, it gains lifelink until end of turn.
Sacrifice Selfless Samurai: Another target creature you control gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Thorough Investigation

Whenever you attack, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you sacrifice a Clue, venture into the dungeon. (Enter the first room or advance to the next room.)

Deflecting Palm

The next time a source of your choice would deal damage to you this turn, prevent that damage. If damage is prevented this way, Deflecting Palm deals that much damage to that source's controller.

Professional Face-Breaker

Menace
Whenever one or more creatures you control deal combat damage to a player, create a Treasure token.
Sacrifice a Treasure: Exile the top card of your library. You may play that card this turn.

Sword of the Animist

Equipped creature gets +1/+1.
Whenever equipped creature attacks, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Equip {2}

Mothrider Samurai

Flying
Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)

Imperial Subduer

Whenever a Samurai or Warrior you control attacks alone, tap target creature you don't control.

Heiko Yamazaki, the General

Trample
Whenever a Samurai or Warrior you control attacks alone, you may cast target artifact card from your graveyard this turn.

Caesar, Legion's Emperor

Whenever you attack, you may sacrifice another creature. When you do, choose two —
• Create two 1/1 red and white Soldier creature tokens with haste that are tapped and attacking.
• You draw a card and you lose 1 life.
• Caesar, Legion's Emperor deals damage equal to the number of creature tokens you control to target opponent.

Command Tower

War's Toll

Whenever an opponent taps a land for mana, tap all lands that player controls.
If a creature an opponent controls attacks, all creatures that opponent controls attack if able.

Blade of Selves

Equipped creature has myriad. (Whenever it attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Equip {4}

High Ground

Each creature you control can block an additional creature each combat.

Savai Triome

({T}: Add {R}, {W}, or {B}.)
Savai Triome enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Talisman of Indulgence

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

Pariah's Shield

All damage that would be dealt to you is dealt to equipped creature instead.
Equip {3}

Prosper, Tome-Bound

Deathtouch
Mystic Arcanum — At the beginning of your end step, exile the top card of your library. Until the end of your next turn, you may play that card.
Pact Boon — Whenever you play a card from exile, create a Treasure token.

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.

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.)

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Adaptive Automaton

As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
Other creatures you control of the chosen type get +1/+1.

Acolyte Hybrid

Heavy Rock Cutter — Whenever Acolyte Hybrid attacks, destroy up to one target artifact. If an artifact is destroyed this way, its controller draws a card.

Shattering Spree

Replicate {R} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Destroy target artifact.

Tragic Arrogance

For each player, you choose from among the permanents that player controls an artifact, a creature, an enchantment, and a planeswalker. Then each player sacrifices all other nonland permanents they control.

Warleader's Call

Creatures you control get +1/+1.
Whenever a creature you control enters, Warleader's Call deals 1 damage to each opponent.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Pact Weapon

As long as Pact Weapon is attached to a creature, you don't lose the game for having 0 or less life.
Whenever equipped creature attacks, draw a card and reveal it. The creature gets +X/+X until end of turn and you lose X life, where X is that card's mana value.
Equip—Discard a card.

Night's Whisper

Ancestral Katana

Whenever a Samurai or Warrior you control attacks alone, you may pay {1}. When you do, attach Ancestral Katana to it.
Equipped creature gets +2/+1.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Search the Premises

Whenever a creature attacks you or a planeswalker you control, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Rakdos Signet

Armory of Iroas

Whenever equipped creature attacks, put a +1/+1 counter on it.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Thunder Lasso

When Thunder Lasso enters, attach it to target creature you control.
Equipped creature gets +1/+1.
Whenever equipped creature attacks, tap target creature defending player controls.
Equip {2}

Karazikar, the Eye Tyrant

Whenever you attack a player, tap target creature that player controls and goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)
Whenever an opponent attacks another one of your opponents, you and the attacking player each draw a card and lose 1 life.