Hostility

Haste
If a spell you control would deal damage to an opponent, prevent that damage. Create a 3/1 red Elemental Shaman creature token with haste for each 1 damage prevented this way.
When Hostility is put into a graveyard from anywhere, shuffle it into its owner's library.

Flamekin Harbinger

When this creature enters, you may search your library for an Elemental card, reveal it, then shuffle and put that card on top.

Repeated Reverberation

When you next cast an instant spell, cast a sorcery spell, or activate a loyalty ability this turn, copy that spell or ability twice. You may choose new targets for the copies.

Slaying Fire

Slaying Fire deals 3 damage to any target.
Adamant — If at least three red mana was spent to cast this spell, it deals 4 damage instead.

Mountain

Demonfire

Demonfire deals X damage to any target. If a creature dealt damage this way would die this turn, exile it instead.
Hellbent — If you have no cards in hand, this spell can't be countered and the damage can't be prevented.

Banefire

Banefire deals X damage to any target.
If X is 5 or more, this spell can't be countered and the damage can't be prevented.

Thawing Glaciers

This land enters tapped.
{1}, {T}: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle. Return this land to its owner's hand at the beginning of the next cleanup step.

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.