Field Marshal

Other Soldier creatures get +1/+1 and have first strike. (They deal combat damage before creatures without first strike.)

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Tajic, Legion's Edge

Haste
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Prevent all noncombat damage that would be dealt to other creatures you control.
{R}{W}: Tajic, Legion's Edge gains first strike until end of turn.

Rhox Pikemaster

First strike (This creature deals combat damage before creatures without first strike.)
Other Soldier creatures you control have first strike.

Captain of the Watch

Vigilance (Attacking doesn't cause this creature to tap.)
Other Soldier creatures you control get +1/+1 and have vigilance.
When Captain of the Watch enters, create three 1/1 white Soldier creature tokens.

Veteran Armorsmith

Other Soldier creatures you control get +0/+1.

Catapult Master

Tap five untapped Soldiers you control: Exile target creature.

Valiant Veteran

Other Soldiers you control get +1/+1.
{3}{W}{W}, Exile Valiant Veteran from your graveyard: Put a +1/+1 counter on each Soldier you control.

Rescue Retriever

Flash
When Rescue Retriever enters, put a +1/+1 counter on each other Soldier you control.
Prevent all damage that would be dealt to other attacking Soldiers you control.

Veteran Swordsmith

Other Soldier creatures you control get +1/+0.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Commander Mustard

Vigilance
Other Soldiers you control have vigilance, trample, and haste.
{2}{R}{W}: Until end of turn, Soldiers you control gain "Whenever this creature attacks, it deals 1 damage to defending player."

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.