Karlach, Fury of Avernus

Whenever you attack, if it's the first combat phase of the turn, untap all attacking creatures. They gain first strike until end of turn. After this phase, there is an additional combat phase.
Choose a Background (You can have a Background as a second commander.)

Aggravated Assault

{3}{R}{R}: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Secure the Wastes

Create X 1/1 white Warrior creature tokens.

Plains

Aurelia, Exemplar of Justice

Flying
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, choose up to one target creature you control. Until end of turn, that creature gets +2/+0, gains trample if it's red, and gains vigilance if it's white.

Command Tower

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

Idyllic Tutor

Search your library for an enchantment card, reveal it, put it into your hand, then shuffle.

Intangible Virtue

Creature tokens you control get +1/+1 and have vigilance.

Odric, Master Tactician

First strike (This creature deals combat damage before creatures without first strike.)
Whenever Odric, Master Tactician and at least three other creatures attack, you choose which creatures block this combat and how those creatures block.

Kor Celebrant

Whenever Kor Celebrant or another creature you control enters, you gain 1 life.

Mountain

Disrupt Decorum

Goad all creatures you don't control. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)

Gimli, Counter of Kills

Trample
Whenever a creature an opponent controls dies, Gimli, Counter of Kills deals 1 damage to that creature's controller.

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, Mana Crypt deals 3 damage to you.
{T}: Add {C}{C}.

Outlaws' Merriment

At the beginning of your upkeep, choose one at random. Create a red and white creature token with those characteristics.
• 3/1 Human Warrior with trample and haste.
• 2/1 Human Cleric with lifelink and haste.
• 1/2 Human Rogue with haste and "When this creature enters, it deals 1 damage to any target."

Furnace-Blessed Conqueror

Whenever Furnace-Blessed Conqueror attacks, create a tapped and attacking token that's a copy of it. Put a +1/+1 counter on that token for each +1/+1 counter on Furnace-Blessed Conqueror. Sacrifice that token at the beginning of the next end step.

Sun-Blessed Guardian

{5}{R/P}: Transform Sun-Blessed Guardian. Activate only as a sorcery. ({R/P} can be paid with either {R} or 2 life.)

Sun-Blessed Guardian // Furnace-Blessed Conqueror

Loyal Unicorn

Vigilance
Lieutenant — At the beginning of combat on your turn, if you control your commander, prevent all combat damage that would be dealt to creatures you control this turn. Other creatures you control gain vigilance until end of turn.

Taunt from the Rampart

Goad all creatures your opponents control. Until your next turn, those creatures can't block. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Angrath's Marauders

If a source you control would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.

Everybody Lives!

All creatures gain hexproof and indestructible until end of turn. Players gain hexproof until end of turn. Players can't lose life this turn and players can't lose the game or win the game this turn.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Neheb, the Eternal

Afflict 3 (Whenever this creature becomes blocked, defending player loses 3 life.)
At the beginning of each of your postcombat main phases, add {R} for each 1 life your opponents have lost this turn.

War of the Last Alliance

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Search your library for a legendary creature card, reveal it, put it into your hand, then shuffle.
III — Creatures you control gain double strike until end of turn. The Ring tempts you.

Warleader's Call

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

Rekindling Phoenix

Flying
When Rekindling Phoenix dies, create a 0/1 red Elemental creature token with "At the beginning of your upkeep, sacrifice this creature and return target card named Rekindling Phoenix from your graveyard to the battlefield. It gains haste until end of turn."

Phoenix of Ash

Flying, haste
{2}{R}: Phoenix of Ash gets +2/+0 until end of turn.
Escape—{2}{R}{R}, Exile three other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)
Phoenix of Ash escapes with a +1/+1 counter on it.

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.)

Akroan Hoplite

Whenever Akroan Hoplite attacks, it gets +X/+0 until end of turn, where X is the number of attacking creatures you control.

Arcane Signet

Rising of the Day

Creatures you control have haste.
Legendary creatures you control get +1/+0.

Elenda's Hierophant

Flying
Whenever you gain life, put a +1/+1 counter on Elenda's Hierophant.
When Elenda's Hierophant dies, create X 1/1 white Vampire creature tokens with lifelink, where X is its power.

Gather the Townsfolk

Create two 1/1 white Human creature tokens.
Fateful hour — If you have 5 or less life, create five of those tokens instead.

Basilisk Collar

Equipped creature has deathtouch and lifelink.
Equip {2}

Sun Titan

Vigilance
Whenever Sun Titan enters or attacks, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

Aurelia, the Warleader

Flying, vigilance, haste
Whenever Aurelia, the Warleader attacks for the first time each turn, untap all creatures you control. After this phase, there is an additional combat phase.

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.

Aurelia, the Law Above

Flying, vigilance, haste
Whenever a player attacks with three or more creatures, you draw a card.
Whenever a player attacks with five or more creatures, Aurelia, the Law Above deals 3 damage to each of your opponents and you gain 3 life.

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.

Odric, Lunarch Marshal

At the beginning of each combat, creatures you control gain first strike until end of turn if a creature you control has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, skulk, trample, and vigilance.

Valkyrie Harbinger

Flying, lifelink
At the beginning of each end step, if you gained 4 or more life this turn, create a 4/4 white Angel creature token with flying and vigilance.

Crescendo of War

At the beginning of each upkeep, put a strife counter on Crescendo of War.
Attacking creatures get +1/+0 for each strife counter on Crescendo of War.
Blocking creatures you control get +1/+0 for each strife counter on Crescendo of War.

Sunhome Guildmage

{1}{R}{W}: Creatures you control get +1/+0 until end of turn.
{2}{R}{W}: Create a 1/1 red and white Soldier creature token with haste.

Make a Stand

Creatures you control get +1/+0 and gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Waves of Aggression

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Samwise the Stouthearted

Flash
When Samwise the Stouthearted enters, choose up to one target permanent card in your graveyard that was put there from the battlefield this turn. Return it to your hand. Then the Ring tempts you.

Blazing Archon

Varchild, Betrayer of Kjeldor

Whenever Varchild, Betrayer of Kjeldor deals combat damage to a player, that player creates that many 1/1 red Survivor creature tokens.
Survivors your opponents control can't block, and they can't attack you or planeswalkers you control.
When Varchild leaves the battlefield, gain control of all Survivors.

Firemane Avenger

Flying
Battalion — Whenever Firemane Avenger and at least two other creatures attack, Firemane Avenger deals 3 damage to any target and you gain 3 life.

Forth Eorlingas!

Create X 2/2 red Human Knight creature tokens with trample and haste.
Whenever one or more creatures you control deal combat damage to one or more players this turn, you become the monarch.

Serra's Guardian

Flying (This creature can't be blocked except by creatures with flying or reach.)
Vigilance (Attacking doesn't cause this creature to tap.)
Other creatures you control have vigilance.

Sol Ring

Deploy to the Front

Create X 1/1 white Soldier creature tokens, where X is the number of creatures on the battlefield.

Storm Herd

Create X 1/1 white Pegasus creature tokens with flying, where X is your life total.

Immortal Phoenix

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Immortal Phoenix dies, return it to its owner's hand.

Devilish Valet

Trample, haste
Alliance — Whenever another creature you control enters, double Devilish Valet's power until end of turn.

Rhox Faithmender

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
If you would gain life, you gain twice that much life instead.

Congregate

Target player gains 2 life for each creature on the battlefield.

Tajic, Blade of the Legion

Indestructible
Battalion — Whenever Tajic, Blade of the Legion and at least two other creatures attack, Tajic gets +5/+5 until end of turn.

Urabrask the Hidden

Creatures you control have haste.
Creatures your opponents control enter tapped.

Song of the Worldsoul

Whenever you cast a spell, populate. (Create a token that's a copy of a creature token you control.)

Exotic Orchard

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

Hero of the Nyxborn

When Hero of the Nyxborn enters, create a 1/1 white Human Soldier creature token.
Whenever you cast a spell that targets Hero of the Nyxborn, creatures you control get +1/+0 until end of turn.

Firewing Phoenix

Flying
{1}{R}{R}{R}: Return Firewing Phoenix from your graveyard to your hand.

Moraug, Fury of Akoum

Each creature you control gets +1/+0 for each time it has attacked this turn.
Landfall — Whenever a land you control enters, if it's your main phase, there's an additional combat phase after this phase. At the beginning of that combat, untap all creatures you control.