Witty Roastmaster

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

Gibbering Fiend

When Gibbering Fiend enters, it deals 1 damage to each opponent.
Delirium — At the beginning of each opponent's upkeep, if there are four or more card types among cards in your graveyard, Gibbering Fiend deals 1 damage to that player.

Terror of the Peaks

Flying
Spells your opponents cast that target Terror of the Peaks cost an additional 3 life to cast.
Whenever another creature you control enters, Terror of the Peaks deals damage equal to that creature's power to any target.

Forgeborn Oreads

Constellation — Whenever Forgeborn Oreads or another enchantment you control enters, Forgeborn Oreads deals 1 damage to any target.

Grasping Thrull

Flying
When Grasping Thrull enters, it deals 2 damage to each opponent and you gain 2 life.

Ghitu Journeymage

When Ghitu Journeymage enters, if you control another Wizard, Ghitu Journeymage deals 2 damage to each opponent.

Storm Caller

When Storm Caller enters, it deals 2 damage to each opponent.

Goblin Chainwhirler

First strike
When Goblin Chainwhirler enters, it deals 1 damage to each opponent and each creature and planeswalker they control.

Lavabelly Sliver

Sliver creatures you control have "When this creature enters, it deals 1 damage to target player or planeswalker and you gain 1 life."

Scourge of Valkas

Flying
Whenever Scourge of Valkas or another Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn.

Purphoros, God of the Forge

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature you control enters, Purphoros deals 2 damage to each opponent.
{2}{R}: Creatures you control get +1/+0 until end of turn.

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, Rose Room Treasurer deals X damage to any target.

Where Ancients Tread

Whenever a creature you control with power 5 or greater enters, you may have Where Ancients Tread deal 5 damage to any target.

Heart-Piercer Manticore

When Heart-Piercer Manticore enters, you may sacrifice another creature. When you do, Heart-Piercer Manticore deals damage equal to that creature's power to any target.
Embalm {5}{R} ({5}{R}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Manticore with no mana cost. Embalm only as a sorcery.)

Gruesome Scourger

When Gruesome Scourger enters, it deals damage to target opponent or planeswalker equal to the number of creatures you control.

Forerunner of the Empire

When Forerunner of the Empire enters, you may search your library for a Dinosaur card, reveal it, then shuffle and put that card on top.
Whenever a Dinosaur you control enters, you may have Forerunner of the Empire deal 1 damage to each creature.

Inferno Titan

{R}: Inferno Titan gets +1/+0 until end of turn.
Whenever Inferno Titan enters or attacks, it deals 3 damage divided as you choose among one, two, or three targets.

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Foundry Champion

When Foundry Champion enters, it deals damage to any target equal to the number of creatures you control.
{R}: Foundry Champion gets +1/+0 until end of turn.
{W}: Foundry Champion gets +0/+1 until end of turn.

Reckless Fireweaver

Whenever an artifact you control enters, Reckless Fireweaver deals 1 damage to each opponent.

Lukka, Wayward Bonder

+1: You may discard a card. If you do, draw a card. If a creature card was discarded this way, draw two cards instead.
−2: Return target creature card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of your next upkeep.
−7: You get an emblem with "Whenever a creature you control enters, it deals damage equal to its power to any target."

Mila, Crafty Companion

Whenever an opponent attacks one or more planeswalkers you control, put a loyalty counter on each planeswalker you control.
Whenever a permanent you control becomes the target of a spell or ability an opponent controls, you may draw a card.

Mila, Crafty Companion // Lukka, Wayward Bonder

Invader Parasite

Imprint — When Invader Parasite enters, exile target land.
Whenever a land an opponent controls with the same name as the exiled card enters, Invader Parasite deals 2 damage to that player.

Reclusive Artificer

Haste (This creature can attack and {T} as soon as it comes under your control.)
When Reclusive Artificer enters, you may have it deal damage to target creature equal to the number of artifacts you control.

Impact Tremors

Whenever a creature you control enters, Impact Tremors deals 1 damage to each opponent.

Murderous Redcap

When Murderous Redcap enters, it deals damage equal to its power to any target.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Fanatic of Mogis

When Fanatic of Mogis enters, it deals damage to each opponent equal to your devotion to red. (Each {R} in the mana costs of permanents you control counts toward your devotion to red.)

Kessig Malcontents

When Kessig Malcontents enters, it deals damage to target player or planeswalker equal to the number of Humans you control.

Dragon Tempest

Whenever a creature you control with flying enters, it gains haste until end of turn.
Whenever a Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.