Embercleave

Flash
This spell costs {1} less to cast for each attacking creature you control.
When Embercleave enters, attach it to target creature you control.
Equipped creature gets +1/+1 and has double strike and trample.
Equip {3}

Skewer the Critics

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Skewer the Critics deals 3 damage to any target.

Mutavault

{T}: Add {C}.
{1}: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.

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.)

Ramunap Ruins

{T}: Add {C}.
{T}, Pay 1 life: Add {R}.
{2}{R}{R}, {T}, Sacrifice a Desert: Ramunap Ruins deals 2 damage to each opponent.

Mountain

Roil Eruption

Kicker {5} (You may pay an additional {5} as you cast this spell.)
Roil Eruption deals 3 damage to any target. If this spell was kicked, it deals 5 damage instead.

Rampaging Ferocidon

Menace
Players can't gain life.
Whenever another creature enters, Rampaging Ferocidon deals 1 damage to that creature's controller.

Foundry Street Denizen

Whenever another red creature you control enters, Foundry Street Denizen gets +1/+0 until end of turn.

Monastery Swiftspear

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Stomp

Damage can't be prevented this turn. Stomp deals 2 damage to any target.

Bonecrusher Giant

Whenever Bonecrusher Giant becomes the target of a spell, Bonecrusher Giant deals 2 damage to that spell's controller.

Bonecrusher Giant // Stomp

Earthshaker Khenra

Haste
When Earthshaker Khenra enters, target creature with power less than or equal to Earthshaker Khenra's power can't block this turn.
Eternalize {4}{R}{R} ({4}{R}{R}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Jackal Warrior with no mana cost. Eternalize only as a sorcery.)

Boulder Rush

Target creature gets +2/+0 until end of turn. (Then exile this card. You may cast the creature later from exile.)