Boros Elite

Battalion — Whenever Boros Elite and at least two other creatures attack, Boros Elite gets +2/+2 until end of turn.

Truefire Paladin

Vigilance
{R}{W}: Truefire Paladin gets +2/+0 until end of turn.
{R}{W}: Truefire Paladin gains first strike until end of turn.

Plains

Fortress Cyclops

Whenever Fortress Cyclops attacks, it gets +3/+0 until end of turn.
Whenever Fortress Cyclops blocks, it gets +0/+3 until end of turn.

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.

Frontline Medic

Battalion — Whenever Frontline Medic and at least two other creatures attack, creatures you control gain indestructible until end of turn.
Sacrifice Frontline Medic: Counter target spell with {X} in its mana cost unless its controller pays {3}.

Wojek Halberdiers

Battalion — Whenever Wojek Halberdiers and at least two other creatures attack, Wojek Halberdiers gains first strike until end of turn.

Mountain

Bomber Corps

Battalion — Whenever Bomber Corps and at least two other creatures attack, Bomber Corps deals 1 damage to any target.

Assemble the Legion

At the beginning of your upkeep, put a muster counter on Assemble the Legion. Then create a 1/1 red and white Soldier creature token with haste for each muster counter on Assemble the Legion.

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.

Boros Guildgate

Boros Guildgate enters tapped.
{T}: Add {R} or {W}.

Daring Skyjek

Battalion — Whenever Daring Skyjek and at least two other creatures attack, Daring Skyjek gains flying until end of turn.