Neck Breaker

Attacking creatures you control get +1/+0 and have trample.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Neck Breaker.

Breakneck Rider

At the beginning of each upkeep, if no spells were cast last turn, transform Breakneck Rider.

Breakneck Rider // Neck Breaker

Outnumber

Outnumber deals damage to target creature equal to the number of creatures you control.

Lightning Mauler

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Lightning Mauler is paired with another creature, both creatures have haste.

Borderland Marauder

Whenever Borderland Marauder attacks, it gets +2/+0 until end of turn.

Titan of Eternal Fire

Each Human creature you control has "{R}, {T}: This creature deals 1 damage to any target."

Flameheart Werewolf

Whenever Flameheart Werewolf blocks or becomes blocked by a creature, Flameheart Werewolf deals 2 damage to that creature.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Flameheart Werewolf.

Kessig Forgemaster

Whenever Kessig Forgemaster blocks or becomes blocked by a creature, Kessig Forgemaster deals 1 damage to that creature.
At the beginning of each upkeep, if no spells were cast last turn, transform Kessig Forgemaster.

Kessig Forgemaster // Flameheart Werewolf

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.

Kessig Malcontents

When Kessig Malcontents enters, it deals damage to target player or planeswalker equal to the number of Humans you control.

Thriving Bluff

Thriving Bluff enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Stonewright

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Stonewright is paired with another creature, each of those creatures has "{R}: This creature gets +1/+0 until end of turn."

Deem Worthy

Deem Worthy deals 7 damage to target creature.
Cycling {3}{R} ({3}{R}, Discard this card: Draw a card.)
When you cycle Deem Worthy, you may have it deal 2 damage to target creature.

Mountain

Hanweir Garrison

Whenever Hanweir Garrison attacks, create two 1/1 red Human creature tokens that are tapped and attacking.
(Melds with Hanweir Battlements.)

Riot Ringleader

Whenever Riot Ringleader attacks, Human creatures you control get +1/+0 until end of turn.