Hagi Mob

Boast — {1}{R}: This creature deals 1 damage to any target. (Activate only if this creature attacked this turn and only once each turn.)

Duskwielder

Boast — {1}: Target opponent loses 1 life and you gain 1 life. (Activate only if this creature attacked this turn and only once each turn.)

Kardur, Doomscourge

When Kardur enters, until your next turn, creatures your opponents control attack each combat if able and attack a player other than you if able.
Whenever an attacking creature dies, each opponent loses 1 life and you gain 1 life.

Swamp

Alexios, Deimos of Kosmos

Trample
Alexios attacks each combat if able, can't be sacrificed, and can't attack its owner.
At the beginning of each player's upkeep, that player gains control of Alexios, untaps it, and puts a +1/+1 counter on it. It gains haste until end of turn.

Dolmen Gate

Prevent all combat damage that would be dealt to attacking creatures you control.

Lovisa Coldeyes

Each creature that's a Barbarian, a Warrior, or a Berserker gets +2/+2 and has haste.

Door of Destinies

As this artifact enters, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on this artifact.
Creatures you control of the chosen type get +1/+1 for each charge counter on this artifact.

Fearless Pup

First strike
Boast — {2}{R}: This creature gets +2/+0 until end of turn. (Activate only if this creature attacked this turn and only once each turn.)

Patchwork Banner

As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{T}: Add one mana of any color.

Garna, Bloodfist of Keld

Whenever another creature you control dies, draw a card if it was attacking. Otherwise, Garna deals 1 damage to each opponent.

Bloodfell Caves

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {B} or {R}.

Treasure

{T}, Sacrifice this token: Add one mana of any color.

Skemfar Avenger

Whenever another nontoken Elf or Berserker you control dies, you draw a card and you lose 1 life.

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Demon Berserker

Menace (This creature can't be blocked except by two or more creatures.)

Great Train Heist

Spree (Choose one or more additional costs.)
+ {2}{R} — Untap all creatures you control. If it's your combat phase, there is an additional combat phase after this phase.
+ {2} — Creatures you control get +1/+0 and gain first strike until end of turn.
+ {R} — Choose target opponent. Whenever a creature you control deals combat damage to that player this turn, create a tapped Treasure token.

Draugr Recruiter

Boast — {3}{B}: Return target creature card from your graveyard to your hand. (Activate only if this creature attacked this turn and only once each turn.)

Eradicator Valkyrie

Flying, lifelink, hexproof from planeswalkers
Boast — {1}{B}, Sacrifice a creature: Each opponent sacrifices a creature or planeswalker. (Activate only if this creature attacked this turn and only once each turn.)

Varragoth, Bloodsky Sire

Deathtouch
Boast — {1}{B}: Target player searches their library for a card, then shuffles and puts that card on top. (Activate only if this creature attacked this turn and only once each turn.)

The Bloodsky Massacre

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Create a 2/3 red Demon Berserker creature token with menace.
II — Whenever a Berserker attacks this turn, you draw a card and you lose 1 life.
III — Add {R} for each Berserker you control. Until end of turn, you don't lose this mana as steps and phases end.

Harnfel, Horn of Bounty

Discard a card: Exile the top two cards of your library. You may play those cards this turn.

Birgi, God of Storytelling

Whenever you cast a spell, add {R}. Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.

Birgi, God of Storytelling // Harnfel, Horn of Bounty

Frenzied Raider

Whenever you activate a boast ability, put a +1/+1 counter on this creature.

Dragonkin Berserker

First strike
Boast abilities you activate cost {1} less to activate for each Dragon you control.
Boast — {4}{R}: Create a 5/5 red Dragon creature token with flying. (Activate only if this creature attacked this turn and only once each turn.)

Fearless Liberator

Boast — {2}{R}: Create a 2/1 red Dwarf Berserker creature token. (Activate only if this creature attacked this turn and only once each turn.)

Gastal Thrillseeker

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
When this creature enters, it deals 1 damage to target opponent and you gain 1 life.
Max speed — This creature has deathtouch and haste.

Mountain

Rite of Flame

Add {R}{R}, then add {R} for each card named Rite of Flame in each graveyard.

Hardened Berserker

Whenever this creature attacks, the next spell you cast this turn costs {1} less to cast.

Arni Brokenbrow

Haste
Boast — {1}: You may change Arni's base power to 1 plus the greatest power among other creatures you control until end of turn. (Activate only if this creature attacked this turn and only once each turn.)