Brotherhood Headquarters

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast an Assassin spell or a spell that has freerunning, or to activate an ability of an Assassin source.

Monastery Raid

Freerunning {X}{R} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Exile the top two cards of your library. If this spell's freerunning cost was paid, exile the top X cards of your library instead. You may play the exiled cards until the end of your next turn.

Kassandra, Eagle Bearer

Haste
When Kassandra enters, search your graveyard, hand, and library for a card named The Spear of Leonidas, put it onto the battlefield, then shuffle.
Whenever a creature you control with a legendary Equipment attached to it deals combat damage to a player, draw a card.

Brotherhood Regalia

Equipped creature has ward {2}, is an Assassin in addition to its other types, and can't be blocked.
Equip legendary creature {1}
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Spartan Veteran

During your turn, Spartan Veteran has first strike. (It deals combat damage before creatures without first strike.)
{2}: Spartan Veteran gets +1/+0 until end of turn.

Mountain

Hidden Footblade

Flash
When Hidden Footblade enters, attach it to target creature you control. That creature gains first strike until end of turn.
Equipped creature gets +1/+0 and has haste.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Overpowering Attack

Freerunning {2}{R} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Untap all creatures you control that attacked this turn. If it's your main phase, there is an additional combat phase after this phase, followed by an additional main phase.

Arbaaz Mir

Whenever Arbaaz Mir or another nontoken historic permanent you control enters, Arbaaz Mir deals 1 damage to each opponent and you gain 1 life. (Artifacts, legendaries, and Sagas are historic.)

Settlement Blacksmith

When Settlement Blacksmith enters, if you control an Equipment, draw a card.

Templar Knight

Vigilance
{W}, Tap five untapped attacking creatures you control named Templar Knight: Search your library for a legendary artifact card, put it onto the battlefield, then shuffle.
A deck can have any number of cards named Templar Knight.

Surtr, Fiery Jötun

Trample (This creature can deal excess combat damage to the player it's attacking.)
Whenever you cast a historic spell, Surtr, Fiery Jötun deals 3 damage to any target. (Artifacts, legendaries, and Sagas are historic.)

Labyrinth Adversary

Trample (This creature can deal excess combat damage to the player it's attacking.)
Whenever you attack, you may pay {1}{R}. When you do, target creature can't block this turn.

Hidden Blade

Flash
When Hidden Blade enters, attach it to target creature you control. If that creature is an Assassin, it gains deathtouch until end of turn.
Equipped creature gets +1/+0 and has first strike.
Equip {2}

Ezio, Brash Novice

Whenever Ezio, Brash Novice attacks, put a +1/+1 counter on it.
As long as Ezio has two or more counters on it, it has first strike and is an Assassin in addition to its other types.

Towering Viewpoint

Defender, reach
Leap of Faith — {3}: Target creature gains flying until end of turn.

Stone Quarry

Stone Quarry enters tapped.
{T}: Add {R} or {W}.

Hookblade

When Hookblade enters, attach it to target creature you control.
Equipped creature gets +1/+0.
During your turn, equipped creature has flying.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Abstergo Entertainment

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{3}, {T}, Exile Abstergo Entertainment: Return up to one target historic card from your graveyard to your hand, then exile all graveyards. (Artifacts, legendaries, and Sagas are historic.)

Escarpment Fortress

Defender (This creature can't attack.)
Reach (This creature can block creatures with flying.)
Other creatures you control get +1/+0.
Whenever you attack with two or more creatures, draw a card.

Battlefield Improvisation

Target creature gets +2/+2 until end of turn. If that creature is attacking, you may attach any number of Equipment you control to it.

Haystack

{2}, {T}: Target creature you control phases out. (Treat it and anything attached to it as though they don't exist until your next turn.)

Senu, Keen-Eyed Protector

Flying, vigilance
{T}, Exile Senu, Keen-Eyed Protector: You gain 2 life and scry 2.
When a legendary creature you control attacks and isn't blocked, if Senu is exiled, put it onto the battlefield attacking.

Distract the Guards

Freerunning {1}{W} (You may cast this spell for its freerunning cost if you dealt combat damage to a player this turn with an Assassin or commander.)
Create three 1/1 white Human Rogue creature tokens.

Aya of Alexandria

Menace, lifelink
Whenever a historic creature you control deals combat damage to a player, create a 1/1 black Assassin creature token with menace. (Artifacts, legendaries, and Sagas are historic.)

Bureau Headmaster

Equipment spells you cast cost {1} less to cast.
Equip abilities you activate cost {1} less to activate.

Reconstruct History

Return up to one target artifact card, up to one target enchantment card, up to one target instant card, up to one target sorcery card, and up to one target planeswalker card from your graveyard to your hand.
Exile Reconstruct History.

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.

Reconnaissance

{0}: Remove target attacking creature you control from combat and untap it. (If you activate during end of combat, the creature will untap after it deals combat damage.)

Detained by Legionnaires

Enchant creature
Enchanted creature can't attack or block.

The Spear of Leonidas

Whenever equipped creature attacks, choose one —
• Bull Rush — It gains double strike until end of turn.
• Summon — Create Phobos, a legendary 3/2 red Horse creature token.
• Revelation — Discard two cards, then draw two cards.
Equip {2}

Raven Clan War-Axe

When Raven Clan War-Axe enters, you may search your library and/or graveyard for a card named Eivor, Battle-Ready, reveal it, and put it into your hand. If you search your library this way, shuffle.
Equipped creature gets +2/+0 and has trample.
Equip {2}

Misthios's Fury

Misthios's Fury deals 3 damage to target creature. If you control an Equipment, Misthios's Fury also deals 2 damage to that creature's controller.

Bayek of Siwa

Double strike
During your turn, other historic creatures you control have double strike.
Disguise {1}{R}{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.)

Headsplitter

When Headsplitter enters, create a 1/1 black Assassin creature token with menace, then attach Headsplitter to it.
Equipped creature gets +1/+0.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Sunbaked Canyon

{T}, Pay 1 life: Add {R} or {W}.
{1}, {T}, Sacrifice Sunbaked Canyon: Draw a card.

Origin of the Hidden Ones

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Origin of the Hidden Ones deals 4 damage to any target.
II — Create two 1/1 black Assassin creature tokens with menace.
III — Whenever an Assassin you control attacks this turn, create a 1/1 black Assassin creature token with menace that's tapped and attacking.

Cathartic Reunion

As an additional cost to cast this spell, discard two cards.
Draw three cards.

Tax Collector

When Tax Collector enters, choose one —
• Tax — Until your next turn, spells your opponents cast cost {1} more to cast.
• Arrest — Detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

Keen-Eyed Raven

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Keen-Eyed Raven enters, put a +1/+1 counter on another target creature you control.

Smoke Bomb

Flash
All creatures have shroud. (They can't be the targets of spells or abilities.)
At the beginning of your upkeep, sacrifice Smoke Bomb. When you do, target creature you control can't be blocked this turn.

Eivor, Battle-Ready

Vigilance (Attacking doesn't cause this creature to tap.)
Haste (This creature can attack as soon as it comes under your control.)
Whenever Eivor, Battle-Ready attacks, it deals damage equal to the number of Equipment you control to each opponent.