Vial Smasher, Gleeful Grenadier

Whenever another outlaw you control enters, Vial Smasher, Gleeful Grenadier deals 1 damage to target opponent. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)

Steampath Charger

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature dies, it deals 1 damage to target player.

Swamp

The Infamous Cruelclaw

Menace
Whenever The Infamous Cruelclaw deals combat damage to a player, exile cards from the top of your library until you exile a nonland card. You may cast that card by discarding a card rather than paying its mana cost.

Phyrexian Dragon Engine

Double strike
When Phyrexian Dragon Engine enters from your graveyard, you may discard your hand. If you do, draw three cards.
Unearth {3}{R}{R}
(Melds with Mishra, Claimed by Gix.)

Mountain

Lightning Strike

Lightning Strike deals 3 damage to any target.

Shock

Blacksmith's Talent

(Gain the next level as a sorcery to add its ability.)
When Blacksmith's Talent enters, create a colorless Equipment artifact token named Sword with "Equipped creature gets +1/+1" and equip {2}.
{2}{R}: Level 2
At the beginning of combat on your turn, attach target Equipment you control to up to one target creature you control.
{3}{R}: Level 3
During your turn, equipped creatures you control have double strike and haste.

Gev, Scaled Scorch

Ward—Pay 2 life.
Other creatures you control enter with an additional +1/+1 counter on them for each opponent who lost life this turn.
Whenever you cast a Lizard spell, Gev, Scaled Scorch deals 1 damage to target opponent.

Blooming Blast

Gift a Treasure (You may promise an opponent a gift as you cast this spell. If you do, they create a Treasure token before its other effects. It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Blooming Blast deals 2 damage to target creature. If the gift was promised, Blooming Blast also deals 3 damage to that creature's controller.

Rowan, Scion of War

Menace
{T}: Spells you cast this turn that are black and/or red cost {X} less to cast, where X is the amount of life you lost this turn. Activate only as a sorcery.

Kindlespark Duo

{T}: Kindlespark Duo deals 1 damage to target opponent.
Whenever you cast a noncreature spell, untap Kindlespark Duo.

Agate-Blade Assassin

Whenever Agate-Blade Assassin attacks, defending player loses 1 life and you gain 1 life.

Hearthborn Battler

Haste
Whenever a player casts their second spell each turn, Hearthborn Battler deals 2 damage to target opponent.

Mishra, Claimed by Gix

Whenever you attack, each opponent loses X life and you gain X life, where X is the number of attacking creatures. If Mishra, Claimed by Gix and a creature named Phyrexian Dragon Engine are attacking, and you both own and control them, exile them, then meld them into Mishra, Lost to Phyrexia. It enters tapped and attacking.

Cindering Cutthroat

Cindering Cutthroat enters with a +1/+1 counter on it if an opponent lost life this turn.
{1}{B/R}: Cindering Cutthroat gains menace until end of turn. (It can't be blocked except by two or more creatures.)