Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Arid Mesa

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

Crash Through

Creatures you control gain trample until end of turn. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Gut Shot

({R/P} can be paid with either {R} or 2 life.)
Gut Shot deals 1 damage to any target.

Dragon's Rage Channeler

Whenever you cast a noncreature spell, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
Delirium — As long as there are four or more card types among cards in your graveyard, Dragon's Rage Channeler gets +2/+2, has flying, and attacks each combat if able.

Flagstones of Trokair

{T}: Add {W}.
When Flagstones of Trokair is put into a graveyard from the battlefield, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Plains

Den of the Bugbear

If you control two or more other lands, Den of the Bugbear enters the battlefield tapped.
{T}: Add {R}.
{3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

Mountain

Unholy Heat

Unholy Heat deals 2 damage to target creature or planeswalker.
Delirium — Unholy Heat deals 6 damage instead if there are four or more card types among cards in your graveyard.

Monastery Mentor

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, create a 1/1 white Monk creature token with prowess.

Sacred Foundry

({T}: Add {R} or {W}.)
As Sacred Foundry enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Reckless Impulse

Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Crack the Earth

Soul-Scar Mage

Prowess
If a source you control would deal noncombat damage to a creature an opponent controls, put that many -1/-1 counters on that creature instead.