Gastal Thrillseeker

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
When this creature enters, it deals 1 damage to target opponent and you gain 1 life.
Max speed — This creature has deathtouch and haste.

Agate-Blade Assassin

Whenever this creature attacks, defending player loses 1 life and you gain 1 life.

Fireglass Mentor

At the beginning of your second main phase, if an opponent lost life this turn, exile the top two cards of your library. Choose one of them. Until end of turn, you may play that card.

Scorch Spitter

Whenever this creature attacks, it deals 1 damage to the player or planeswalker it's attacking.

Valley Flamecaller

If a Lizard, Mouse, Otter, or Raccoon you control would deal damage to a permanent or player, it deals that much damage plus 1 instead.

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 deals 1 damage to target opponent.

Magebane Lizard

Whenever a player casts a noncreature spell, this creature deals damage to that player equal to the number of noncreature spells they've cast this turn.

Ravine Raider

Menace (This creature can't be blocked except by two or more creatures.)
{1}{B}: This creature gets +1/+1 until end of turn.

Hearthborn Battler

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