Diamond Knight

Vigilance (Attacking doesn't cause this creature to tap.)
As Diamond Knight enters, choose a color.
Whenever you cast a spell of the chosen color, put a +1/+1 counter on Diamond Knight.

Rowan's Stalwarts

When Rowan's Stalwarts enters, you may search your library and/or graveyard for a card named Rowan, Fearless Sparkmage, reveal it, and put it into your hand. If you search your library this way, shuffle.

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.

Dynacharge

Target creature you control gets +2/+0 until end of turn.
Overload {2}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Fervent Champion

First strike, haste
Whenever Fervent Champion attacks, another target attacking Knight you control gets +1/+0 until end of turn.
Equip abilities you activate that target Fervent Champion cost {3} less to activate.

Rowan, Fearless Sparkmage

+1: Up to one target creature gets +3/+0 and gains first strike until end of turn.
−2: Rowan, Fearless Sparkmage deals 1 damage to each of up to two target creatures. Those creatures can't block this turn.
−9: Gain control of all creatures until end of turn. Untap them. They gain haste until end of turn.

Boulder Rush

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

Rimrock Knight

Rimrock Knight // Boulder Rush

Dragon Fodder

Create two 1/1 red Goblin creature tokens.

Mountain

Ogre Errant

Whenever Ogre Errant attacks, another target attacking Knight gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Joust

Choose target creature you control and target creature you don't control. The creature you control gets +2/+1 until end of turn if it's a Knight. Then those creatures fight each other. (Each deals damage equal to its power to the other.)

Embereth Paladin

Haste
Adamant — If at least three red mana was spent to cast this spell, Embereth Paladin enters with a +1/+1 counter on it.