Umori, the Collector

Companion — Each nonland card in your starting deck shares a card type. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
As Umori, the Collector enters the battlefield, choose a card type.
Spells you cast of the chosen type cost {1} less to cast.

Hagra Diabolist

Whenever Hagra Diabolist or another Ally enters the battlefield under your control, you may have target player lose life equal to the number of Allies you control.

Jwari Shapeshifter

You may have Jwari Shapeshifter enter the battlefield as a copy of any Ally creature on the battlefield.

Kalastria Healer

Rally — Whenever Kalastria Healer or another Ally enters the battlefield under your control, each opponent loses 1 life and you gain 1 life.

Kabira Evangel

Whenever Kabira Evangel or another Ally enters the battlefield under your control, you may choose a color. If you do, Allies you control gain protection from the chosen color until end of turn.

Bala Ged Thief

Whenever Bala Ged Thief or another Ally enters the battlefield under your control, target player reveals a number of cards from their hand equal to the number of Allies you control. You choose one of them. That player discards that card.

Rukarumel, Biologist

As Rukarumel, Biologist enters the battlefield, choose a creature type.
Slivers you control and nontoken creatures you control are the chosen type in addition to their other creature types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 1/1 colorless Sliver creature token.

Bruse Tarl, Boorish Herder

Whenever Bruse Tarl, Boorish Herder enters the battlefield or attacks, target creature you control gains double strike and lifelink until end of turn.
Partner (You can have two commanders if both have partner.)

Drana, Liberator of Malakir

Flying, first strike
Whenever Drana, Liberator of Malakir deals combat damage to a player, put a +1/+1 counter on each attacking creature you control.

Harabaz Druid

{T}: Add X mana of any one color, where X is the number of Allies you control.

Agadeem Occultist

{T}: Put target creature card from an opponent's graveyard onto the battlefield under your control if its mana value is less than or equal to the number of Allies you control.

General Tazri

When General Tazri enters the battlefield, you may search your library for an Ally creature card, reveal it, put it into your hand, then shuffle.
{W}{U}{B}{R}{G}: Ally creatures you control get +X/+X until end of turn, where X is the number of colors among those creatures.

Akoum Battlesinger

Haste
Whenever Akoum Battlesinger or another Ally enters the battlefield under your control, you may have Ally creatures you control get +1/+0 until end of turn.

Beastcaller Savant

Haste
{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Drana's Chosen

Cohort — {T}, Tap an untapped Ally you control: Create a tapped 2/2 black Zombie creature token.