Seascape Aerialist

Whenever Seascape Aerialist or another Ally enters the battlefield under your control, you may have Ally creatures you control gain flying until end of turn.

Ondu Cleric

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

Weapons Trainer

Other creatures you control get +1/+0 as long as you control an Equipment.

Jwari Shapeshifter

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

Serene Steward

Whenever you gain life, you may pay {W}. If you do, put a +1/+1 counter on target creature.

Tajuru Warcaller

Rally — Whenever Tajuru Warcaller or another Ally enters the battlefield under your control, creatures you control get +2/+2 until end of turn.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Umara Raptor

Flying
Whenever Umara Raptor or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Umara Raptor.

Turntimber Ranger

Whenever Turntimber Ranger or another Ally enters the battlefield under your control, you may create a 2/2 green Wolf creature token. If you do, put a +1/+1 counter on Turntimber Ranger.

Tajuru Archer

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

Kor Scythemaster

Kor Scythemaster has first strike as long as it's attacking.

Mirror Shield

Equipped creature gets +0/+2 and has hexproof and "Whenever a creature with deathtouch blocks or becomes blocked by this creature, destroy that creature."
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

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.

Stone Haven Outfitter

Equipped creatures you control get +1/+1.
Whenever an equipped creature you control dies, draw a card.

Cliffhaven Vampire

Flying
Whenever you gain life, each opponent loses 1 life.

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.

Makindi Shieldmate

Defender
Whenever Makindi Shieldmate or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Makindi Shieldmate.

Oran-Rief Survivalist

Whenever Oran-Rief Survivalist or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Oran-Rief Survivalist.

Kasla, the Broken Halo

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying, vigilance, haste
Whenever you cast another spell that has convoke, scry 2, then draw a card.

Mask of Avacyn

Equipped creature gets +1/+2 and has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {3}

Tuktuk Grunts

Haste
Whenever Tuktuk Grunts or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Tuktuk Grunts.

Tuktuk Scrapper

Whenever Tuktuk Scrapper or another Ally enters the battlefield under your control, 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.

Basilisk Collar

Equipped creature has deathtouch and lifelink.
Equip {2}

Hero of Goma Fada

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

Kor Bladewhirl

Rally — Whenever Kor Bladewhirl or another Ally enters the battlefield under your control, creatures you control gain first strike until end of turn.

Bloodbond Vampire

Whenever you gain life, put a +1/+1 counter on Bloodbond Vampire.

Helm of the Host

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.
Equip {5}

Sea Gate Loremaster

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

Halimar Tidecaller

When Halimar Tidecaller enters the battlefield, you may return target card with awaken from your graveyard to your hand.
Land creatures you control have flying.

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.

Coastal Piracy

Whenever a creature you control deals combat damage to an opponent, you may draw a card.

Hada Freeblade

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

Joraga Bard

Whenever Joraga Bard or another Ally enters the battlefield under your control, you may have Ally creatures you control gain vigilance until end of turn.

Stoneforge Acolyte

Cohort — {T}, Tap an untapped Ally you control: Look at the top four cards of your library. You may reveal an Equipment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Kazandu Blademaster

First strike, vigilance
Whenever Kazandu Blademaster or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Kazandu Blademaster.

Vastwood Animist

{T}: Target land you control becomes an X/X Elemental creature until end of turn, where X is the number of Allies you control. It's still a land.

Bojuka Brigand

Bojuka Brigand can't block.
Whenever Bojuka Brigand or another Ally enters the battlefield under your control, you may put a +1/+1 counter on Bojuka Brigand.

Munda's Vanguard

Cohort — {T}, Tap an untapped Ally you control: Put a +1/+1 counter on each creature you control.

Talus Paladin

Whenever Talus Paladin or another Ally enters the battlefield under your control, you may have Allies you control gain lifelink until end of turn, and you may put a +1/+1 counter on Talus Paladin.

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.

Makindi Patrol

Rally — Whenever Makindi Patrol or another Ally enters the battlefield under your control, creatures you control gain vigilance until end of turn.

Halimar Excavator

Whenever Halimar Excavator or another Ally enters the battlefield under your control, target player mills X cards, where X is 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.