Cloakwood Swarmkeeper

Gathered Swarm — Whenever one or more tokens you control enter, put a +1/+1 counter on Cloakwood Swarmkeeper.

Ninth Bridge Patrol

Whenever another creature you control leaves the battlefield, put a +1/+1 counter on Ninth Bridge Patrol.

Kronch Wrangler

Trample
Whenever a creature you control with power 4 or greater enters, put a +1/+1 counter on Kronch Wrangler.

Savior of the Sleeping

Vigilance
Whenever an enchantment you control is put into a graveyard from the battlefield, put a +1/+1 counter on Savior of the Sleeping.

Umara Raptor

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

Spellgorger Weird

Whenever you cast a noncreature spell, put a +1/+1 counter on Spellgorger Weird.

Blood Researcher

Menace (This creature can't be blocked except by two or more creatures.)
Whenever you gain life, put a +1/+1 counter on Blood Researcher.

Quandrix Pledgemage

Magecraft — Whenever you cast or copy an instant or sorcery spell, put a +1/+1 counter on Quandrix Pledgemage.

Elvish Vanguard

Whenever another Elf enters, put a +1/+1 counter on Elvish Vanguard.

Chicken Troupe

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
When Chicken Troupe enters, you get {TK}, then you may put a sticker on a nonland permanent you own.

Rot Shambler

Whenever another creature you control dies, put a +1/+1 counter on Rot Shambler.

Rising Populace

Whenever another creature or planeswalker you control dies, put a +1/+1 counter on Rising Populace.

Advocate of the Beast

At the beginning of your end step, put a +1/+1 counter on target Beast creature you control.

Novice Dissector

{1}, Sacrifice another creature: Put a +1/+1 counter on target creature. Activate only as a sorcery.

Wirewood Savage

Whenever a Beast enters, you may draw a card.

Wee Champion

Whenever you place a sticker, Wee Champion gets +1/+1 until end of turn. If it's an art sticker, instead put a +1/+1 counter on Wee Champion.

Atomwheel Acrobats

Whenever you roll a 1 or 2, put that many +1/+1 counters on Atomwheel Acrobats.
{2}{G}: Roll a six-sided die.

Oran-Rief Survivalist

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

Chance-Met Elves

Whenever you scry, put a +1/+1 counter on Chance-Met Elves. This ability triggers only once each turn.

Jungle Delver

{3}{G}: Put a +1/+1 counter on Jungle Delver.

Toadstool Admirer

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
{3}{G}: Put a +1/+1 counter on Toadstool Admirer.

Celebrity Fencer

Alliance — Whenever another creature you control enters, put a +1/+1 counter on Celebrity Fencer.

Slumbering Keepguard

Whenever an enchantment you control enters, scry 1.
{2}{W}: Slumbering Keepguard gets +1/+1 until end of turn for each enchantment you control.

Ivy Lane Denizen

Whenever another green creature you control enters, put a +1/+1 counter on target creature.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on Celestial Unicorn.

Makindi Shieldmate

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

Stormkeld Prowler

Whenever you cast a spell with mana value 5 or greater, put two +1/+1 counters on Stormkeld Prowler.