Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Torbran, Thane of Red Fell

If a red source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 2 instead.

Akki Coalflinger

First strike
{R}, {T}: Attacking creatures gain first strike until end of turn.

Acolyte of the Inferno

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever Acolyte of the Inferno becomes blocked by a creature, it deals 2 damage to that creature.

Aetherflame Wall

Defender
Aetherflame Wall can block creatures with shadow as though they didn't have shadow.
{R}: Aetherflame Wall gets +1/+0 until end of turn.

Shock

Aether Flash

Whenever a creature enters, Aether Flash deals 2 damage to it.

Acidic Soil

Acidic Soil deals damage to each player equal to the number of lands they control.

Mountain

Aether Sting

Whenever an opponent casts a creature spell, Aether Sting deals 1 damage to that player.