Hada Freeblade

Whenever Hada Freeblade or another Ally you control enters, you may put a +1/+1 counter on Hada Freeblade.

Realmwalker

Changeling (This card is every creature type.)
As Realmwalker enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

Jwari Shapeshifter

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

Tajuru Archer

Whenever Tajuru Archer or another Ally you control enters, you may have Tajuru Archer deal damage to target creature with flying equal to the number of Allies you control.

Conjurer's Closet

At the beginning of your end step, you may exile target creature you control, then return that card to the battlefield under your control.

Bala Ged Thief

Whenever Bala Ged Thief or another Ally you control enters, 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.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Tuktuk Scrapper

Whenever Tuktuk Scrapper or another Ally you control enters, you may destroy target artifact. If that artifact is put into a graveyard this way, Tuktuk Scrapper deals damage to that artifact's controller equal to the number of Allies you control.

Hero of Goma Fada

Rally — Whenever Hero of Goma Fada or another Ally you control enters, creatures you control gain indestructible until end of turn.

Plains

Rally the Ancestors

Return each creature card with mana value X or less from your graveyard to the battlefield. Exile those creatures at the beginning of your next upkeep. Exile Rally the Ancestors.

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Ondu Cleric

Whenever Ondu Cleric or another Ally you control enters, you may gain life equal to the number of Allies you control.

Eerie Interlude

Exile any number of target creatures you control. Return those cards to the battlefield under their owner's control at the beginning of the next end step.

Forest

Gideon, Ally of Zendikar

+1: Until end of turn, Gideon, Ally of Zendikar becomes a 5/5 Human Soldier Ally creature with indestructible that's still a planeswalker. Prevent all damage that would be dealt to him this turn.
0: Create a 2/2 white Knight Ally creature token.
−4: You get an emblem with "Creatures you control get +1/+1."

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.

Sea Gate Loremaster

{T}: Draw a card for each Ally you control.

Unclaimed Territory

As Unclaimed Territory enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Descendants' Path

At the beginning of your upkeep, reveal the top card of your library. If it's a creature card that shares a creature type with a creature you control, you may cast it without paying its mana cost. If you don't cast it, put it on the bottom of your library.

General Tazri

When General Tazri enters, 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.

Kabira Evangel

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

Island

Collected Company

Look at the top six cards of your library. Put up to two creature cards with mana value 3 or less from among them onto the battlefield. Put the rest on the bottom of your library in any order.

Hagra Diabolist

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

Ally Encampment

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast an Ally spell.
{1}, {T}, Sacrifice Ally Encampment: Return target Ally you control to its owner's hand.

Harabaz Druid

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

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.

Halimar Excavator

Whenever Halimar Excavator or another Ally you control enters, target player mills X cards, where X is the number of Allies you control.