Wildborn Preserver

Flash (You may cast this spell any time you could cast an instant.)
Reach (This creature can block creatures with flying.)
Whenever another non-Human creature you control enters, you may pay {X}. When you do, put X +1/+1 counters on this creature.

Prosperous Innkeeper

When this creature enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Whenever another creature you control enters, you gain 1 life.

Weftstalker Ardent

Whenever another creature or artifact you control enters, this creature deals 1 damage to each opponent.
Warp {R} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Virulent Emissary

Deathtouch
Whenever another creature you control enters, you gain 1 life.

Verdant Sun's Avatar

Whenever this creature or another creature you control enters, you gain life equal to that creature's toughness.

Abzan Beastmaster

At the beginning of your upkeep, draw a card if you control the creature with the greatest toughness or tied for the greatest toughness.

Arwen, Weaver of Hope

Each other creature you control enters with a number of additional +1/+1 counters on it equal to Arwen's toughness.

Selvala, Heart of the Wilds

Whenever another creature enters, its controller may draw a card if its power is greater than each other creature's power.
{G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.

Ogre Battledriver

Whenever another creature you control enters, that creature gets +2/+0 and gains haste until end of turn. (It can attack and {T} this turn.)

Yorvo, Lord of Garenbrig

Yorvo enters with four +1/+1 counters on it.
Whenever another green creature you control enters, put a +1/+1 counter on Yorvo. Then if that creature's power is greater than Yorvo's power, put another +1/+1 counter on Yorvo.

Bitter Work

Whenever you attack a player with one or more creatures with power 4 or greater, draw a card.
Exhaust — {4}: Earthbend 4. Activate only during your turn. (Target land you control becomes a 0/0 creature with haste that's still a land. Put four +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped. Activate each exhaust ability only once.)

Surrak and Goreclaw

Trample
Other creatures you control have trample.
Whenever another nontoken creature you control enters, put a +1/+1 counter on it. It gains haste until end of turn.

Hamletback Goliath

Whenever another creature enters, you may put X +1/+1 counters on this creature, where X is that creature's power.

Warden of the Grove

At the beginning of your end step, put a +1/+1 counter on this creature.
Whenever another nontoken creature you control enters, it endures X, where X is the number of counters on this creature. (Put X +1/+1 counters on the creature that entered or create an X/X white Spirit creature token.)

Railway Brawler

Reach, trample
Whenever another creature you control enters, put X +1/+1 counters on it, where X is its power.
Plot {3}{G} (You may pay {3}{G} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Primal Forcemage

Whenever another creature you control enters, that creature gets +3/+3 until end of turn.

Slash, Reptile Rampager

Alliance — Whenever another creature you control enters, Slash deals 2 damage to each opponent.
Whenever Slash attacks, create a 2/2 red Mutant creature token.

Garruk's Packleader

Whenever another creature you control with power 3 or greater enters, you may draw a card.

Sporeback Troll

Graft 2 (This creature enters with two +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{1}{G}: Regenerate target creature with a +1/+1 counter on it.

Soul of the Harvest

Trample
Whenever another nontoken creature you control enters, you may draw a card.

Agate Instigator

Offspring {1}{R} (You may pay an additional {1}{R} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Whenever another creature you control enters, this creature deals 1 damage to each opponent.

Grumgully, the Generous

Each other non-Human creature you control enters with an additional +1/+1 counter on it.

Godtracker of Jund

Whenever a creature you control with power 5 or greater enters, you may put a +1/+1 counter on this creature.

Legolas Greenleaf

Reach
Legolas can't be blocked by creatures with power 2 or less.
Whenever another legendary creature you control enters, put a +1/+1 counter on Legolas.
Whenever Legolas deals combat damage to a player, draw a card.

Raphael, Tough Turtle

Alliance — Whenever another creature you control enters, Raphael deals 1 damage to target opponent.

Keeper of Fables

Whenever one or more non-Human creatures you control deal combat damage to a player, draw a card.

Nikya of the Old Ways

You can't cast noncreature spells.
Whenever you tap a land for mana, add one mana of any type that land produced.

Gruul Ragebeast

Whenever this creature or another creature you control enters, that creature fights target creature an opponent controls.

Owlbear Shepherd

At the beginning of your end step, if creatures you control have total power 8 or greater, draw a card.

Radagast the Brown

Whenever Radagast or another nontoken creature you control enters, look at the top X cards of your library, where X is that creature's mana value. You may reveal a creature card that doesn't share a creature type with a creature you control from among those cards and put it into your hand. Put the rest on the bottom of your library in a random order.

Witty Roastmaster

Alliance — Whenever another creature you control enters, this creature deals 1 damage to each opponent.

Champion of Lambholt

Creatures with power less than this creature's power can't block creatures you control.
Whenever another creature you control enters, put a +1/+1 counter on this creature.

Rose Room Treasurer

Alliance — Whenever another creature you control enters, create a Treasure token if this is the first or second time this ability has resolved this turn. Otherwise, you may pay {X}. When you do, this creature deals X damage to any target.

Primordial Sage

Whenever you cast a creature spell, you may draw a card.

Herd Gnarr

Whenever another creature you control enters, this creature gets +2/+2 until end of turn.

Champions of the Perfect

As an additional cost to cast this spell, behold an Elf and exile it. (Exile an Elf you control or an Elf card from your hand.)
Whenever you cast a creature spell, draw a card.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Heartwood Storyteller

Whenever a player casts a noncreature spell, each of that player's opponents may draw a card.

Renata, Called to the Hunt

Renata's power is equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)
Each other creature you control enters with an additional +1/+1 counter on it.

Thorn Mammoth

Trample
Whenever this creature or another creature you control enters, this creature fights up to one target creature you don't control.

Tromell, Seymour's Butler

Each other nontoken creature you control enters with an additional +1/+1 counter on it.
{1}, {T}: Proliferate X times, where X is the number of nontoken creatures you control that entered this turn. (To proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there.)

Paleoloth

Whenever another creature you control with power 5 or greater enters, you may return target creature card from your graveyard to your hand.

Elegant Entourage

Alliance — Whenever another creature you control enters, target creature other than this creature gets +1/+1 and gains trample until end of turn.

Essence Warden

Whenever another creature enters, you gain 1 life.

Social Climber

Alliance — Whenever another creature you control enters, you gain 1 life.

Beast Whisperer

Whenever you cast a creature spell, draw a card.

Rocksteady, Mutant Marauder

Partner with Bebop, Skull & Crossbones (When this creature enters, target player may put Bebop into their hand from their library, then shuffle.)
Trample
Whenever another nontoken creature you control enters, put a +1/+1 counter on target creature.

Ivy Lane Denizen

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

Enduring Courage

Whenever another creature you control enters, it gets +2/+0 and gains haste until end of turn.
When Enduring Courage dies, if it was a creature, return it to the battlefield under its owner's control. It's an enchantment. (It's not a creature.)