The Brothers' War

Ambush Paratrooper | Creature | Human Soldier | Flash Flying {5}: Creatures you control get +1/+1 until end of turn. | Vladimir Krisetskiy

Phalanx Vanguard | Creature | Human Soldier | Vigilance Whenever an artifact enters the battlefield under your control, Phalanx Vanguard gets +1/+0 until end of turn. | Izzy

Powerstone Engineer | Creature | Human Artificer | When Powerstone Engineer dies, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.") | Dan Scott

Harbin, Vanguard Aviator | Legendary Creature | Human Soldier | Flying Whenever you attack with five or more Soldiers, creatures you control get +1/+1 and gain flying until end of turn. | Kieran Yanner

Yotian Dissident | Creature | Human Artificer | Whenever an artifact enters the battlefield under your control, put a +1/+1 counter on target creature you control. | Steve Prescott