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.)

Flaming Fist

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

Mammoth Umbra

Enchant creature
Enchanted creature gets +3/+3 and has vigilance.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Celestial Mantle

Enchant creature
Enchanted creature gets +3/+3.
Whenever enchanted creature deals combat damage to a player, double its controller's life total.

Sage's Reverie

Enchant creature
When Sage's Reverie enters the battlefield, draw a card for each Aura you control that's attached to a creature.
Enchanted creature gets +1/+1 for each Aura you control that's attached to a creature.

Spirit Mantle

Enchant creature
Enchanted creature gets +1/+1 and has protection from creatures.

Moonsilver Spear

Equipped creature has first strike.
Whenever equipped creature attacks, create a 4/4 white Angel creature token with flying.
Equip {4}

Evolving Wilds

{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Ordeal of Heliod

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Heliod.
When you sacrifice Ordeal of Heliod, you gain 10 life.

Furycalm Snarl

As Furycalm Snarl enters the battlefield, you may reveal a Mountain or Plains card from your hand. If you don't, Furycalm Snarl enters the battlefield tapped.
{T}: Add {R} or {W}.

Mountain

Laccolith Rig

Enchant creature
Whenever enchanted creature becomes blocked, you may have it deal damage equal to its power to target creature. If you do, the first creature assigns no combat damage this turn.

Strength of Isolation

Enchant creature
Enchanted creature gets +1/+2 and has protection from black.
Madness {W} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Moonsilver Key

{1}, {T}, Sacrifice Moonsilver Key: Search your library for an artifact card with a mana ability or a basic land card, reveal it, put it into your hand, then shuffle.

Benevolent Blessing

Flash
Enchant creature
As Benevolent Blessing enters the battlefield, choose a color.
Enchanted creature has protection from the chosen color. This effect doesn't remove Auras and Equipment you control that are already attached to it.

Hedgewitch's Mask

Equipped creature gets +1/+1.
Equipped creature can't be blocked by creatures with power 4 or greater.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

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.)

Cho-Manno's Blessing

Flash
Enchant creature
As Cho-Manno's Blessing enters the battlefield, choose a color.
Enchanted creature has protection from the chosen color. This effect doesn't remove Cho-Manno's Blessing.

Squee's Embrace

Enchant creature
Enchanted creature gets +2/+2.
When enchanted creature dies, return that card to its owner's hand.

Timely Ward

You may cast Timely Ward as though it had flash if it targets a commander.
Enchant creature
Enchanted creature has indestructible.

Pentarch Ward

Enchant creature
As Pentarch Ward enters the battlefield, choose a color.
When Pentarch Ward enters the battlefield, draw a card.
Enchanted creature has protection from the chosen color. This effect doesn't remove Pentarch Ward.

Boros Garrison

Boros Garrison enters the battlefield tapped.
When Boros Garrison enters the battlefield, return a land you control to its owner's hand.
{T}: Add {R}{W}.

Captain's Claws

Equipped creature gets +1/+0.
Whenever equipped creature attacks, create a 1/1 white Kor Ally creature token that's tapped and attacking.
Equip {1}

Kaldra Compleat

Living weapon
Indestructible
Equipped creature gets +5/+5 and has first strike, trample, indestructible, haste, and "Whenever this creature deals combat damage to a creature, exile that creature."
Equip {7}

Shield of Duty and Reason

Enchant creature
Enchanted creature has protection from green and from blue.

Unquestioned Authority

Enchant creature
When Unquestioned Authority enters the battlefield, draw a card.
Enchanted creature has protection from creatures.

Green Ward

Enchant creature
Enchanted creature has protection from green. This effect doesn't remove Green Ward.

Inspiring Leader

Commander creatures you own have "Creature tokens you control get +2/+2."

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

All That Glitters

Enchant creature
Enchanted creature gets +1/+1 for each artifact and/or enchantment you control.

Inviolability

Enchant creature
Prevent all damage that would be dealt to enchanted creature.

Guild Artisan

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, you create two Treasure tokens." (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Shielded by Faith

Enchant creature
Enchanted creature has indestructible.
Whenever a creature enters the battlefield, you may attach Shielded by Faith to that creature.

Bestial Fury

Enchant creature
When Bestial Fury enters the battlefield, draw a card at the beginning of the next turn's upkeep.
Whenever enchanted creature becomes blocked, it gets +4/+0 and gains trample until end of turn.

Sweeping Cleave

Target creature you control gains double strike until end of turn. (Then exile this card. You may cast the artifact later from exile.)

Two-Handed Axe

Whenever equipped creature attacks, double its power until end of turn.
Equip {1}{R}

Two-Handed Axe // Sweeping Cleave

Stoneskin

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

Veteran Soldier

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, for each opponent, create a 1/1 white Soldier creature token that's tapped and attacking that opponent."

Greatsword of Tyr

Whenever equipped creature attacks, put a +1/+1 counter on it and tap up to one target creature defending player controls.
Equip {W} ({W}: Attach to target creature you control. Equip only as a sorcery.)

Blue Ward

Enchant creature
Enchanted creature has protection from blue. This effect doesn't remove Blue Ward.

Command Tower

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

Mantle of the Ancients

Enchant creature you control
When Mantle of the Ancients enters the battlefield, return any number of target Aura and/or Equipment cards from your graveyard to the battlefield attached to enchanted creature.
Enchanted creature gets +1/+1 for each Aura and Equipment attached to it.

Black Ward

Enchant creature
Enchanted creature has protection from black. This effect doesn't remove Black Ward.

Crystal Slipper

Equipped creature gets +1/+0 and has haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Mirror Shield

Equipped creature gets +0/+2 and has hexproof and "Whenever a creature with deathtouch blocks or becomes blocked by this creature, destroy that creature."
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Ward of Lights

You may cast Ward of Lights as though it had flash. If you cast it any time a sorcery couldn't have been cast, the controller of the permanent it becomes sacrifices it at the beginning of the next cleanup step.
Enchant creature
As Ward of Lights enters the battlefield, choose a color.
Enchanted creature has protection from the chosen color. This effect doesn't remove Ward of Lights.

Prismatic Ward

Enchant creature
As Prismatic Ward enters the battlefield, choose a color.
Prevent all damage that would be dealt to enchanted creature by sources of the chosen color.

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}

Holy Avenger

Equipped creature has double strike.
Whenever equipped creature deals combat damage, you may put an Aura card from your hand onto the battlefield attached to it.
Equip {2}{W}

Mantle of Leadership

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Whenever a creature enters the battlefield, enchanted creature gets +2/+2 until end of turn.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Sun Clasp

Enchant creature
Enchanted creature gets +1/+3.
{W}: Return enchanted creature to its owner's hand.

Rabble Rousing

Hideaway 5 (When this enchantment enters the battlefield, look at the top five cards of your library, exile one face down, then put the rest on the bottom in a random order.)
Whenever you attack with one or more creatures, create that many 1/1 green and white Citizen creature tokens. Then if you control ten or more creatures, you may play the exiled card without paying its mana cost.

Call to Serve

Enchant nonblack creature
Enchanted creature gets +1/+2, has flying, and is an Angel in addition to its other types.

Arcane Signet

Noble Heritage

Commander creatures you own have "When this creature enters the battlefield and at the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. For each opponent who does, you gain protection from that player until your next turn." (You can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Sword of Hours

Whenever equipped creature attacks, put a +1/+1 counter on it.
Whenever equipped creature deals combat damage, roll a d12. If the result is greater than the damage dealt or the result is 12, double the number of +1/+1 counters on that creature.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Plains

Myriad Landscape

Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Hedron Archive

{T}: Add {C}{C}.
{2}, {T}, Sacrifice Hedron Archive: Draw two cards.

Sol Ring

Thran Dynamo

Mask of Avacyn

Equipped creature gets +1/+2 and has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {3}

Everflowing Chalice

Multikicker {2} (You may pay an additional {2} any number of times as you cast this spell.)
Everflowing Chalice enters the battlefield with a charge counter on it for each time it was kicked.
{T}: Add {C} for each charge counter on Everflowing Chalice.

Hyena Umbra

Enchant creature
Enchanted creature gets +1/+1 and has first strike.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Ethereal Armor

Enchant creature
Enchanted creature gets +1/+1 for each enchantment you control and has first strike.

On Serra's Wings

Enchant creature
Enchanted creature is legendary, gets +1/+1, and has flying, vigilance, and lifelink.

Armored Ascension

Enchant creature
Enchanted creature gets +1/+1 for each Plains you control and has flying.

Boros Signet

Tavern Brawler

Commander creatures you own have "At the beginning of your upkeep, exile the top card of your library. This creature gets +X/+0 until end of turn, where X is that card's mana value. You may play that card this turn."

Inquisitorial Rosette

Inquisition Agents — Whenever equipped creature attacks, create a 2/2 white Astartes Warrior creature token with vigilance that's attacking. Then attacking creatures gain menace until end of turn.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Boots of Speed

Strength-Testing Hammer

Whenever equipped creature attacks, roll a six-sided die. That creature gets +X/+0 until end of turn, where X is the result. Then if it has the greatest power or is tied for greatest power among creatures on the battlefield, draw a card.
Equip {3}

Kithkin Armor

Enchant creature
Enchanted creature can't be blocked by creatures with power 3 or greater.
Sacrifice Kithkin Armor: The next time a source of your choice would deal damage to enchanted creature this turn, prevent that damage.