Hellspark Elemental

Trample, haste
At the beginning of the end step, sacrifice Hellspark Elemental.
Unearth {1}{R} ({1}{R}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Skullcrack

Players can't gain life this turn. Damage can't be prevented this turn. Skullcrack deals 3 damage to target player or planeswalker.

Spark Elemental

Trample, haste (This creature can deal excess combat damage to the player or planeswalker it's attacking. This creature can attack and {T} as soon as it comes under your control.)
At the beginning of the end step, sacrifice Spark Elemental.

Guttersnipe

Whenever you cast an instant or sorcery spell, this creature deals 2 damage to each opponent.

Fireblast

You may sacrifice two Mountains rather than pay this spell's mana cost.
Fireblast deals 4 damage to any target.

Jaya's Greeting

Jaya's Greeting deals 3 damage to target creature. Scry 1.

Play with Fire

Play with Fire deals 2 damage to any target. If a player is dealt damage this way, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Slith Firewalker

Haste
Whenever Slith Firewalker deals combat damage to a player, put a +1/+1 counter on it.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Rite of Flame

Add {R}{R}, then add {R} for each card named Rite of Flame in each graveyard.

Magma Jet

Magma Jet deals 2 damage to any target. Scry 2.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Thermo-Alchemist

Defender
{T}: Thermo-Alchemist deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap Thermo-Alchemist.