Daring Escape

Target creature gets +1/+0 and gains first strike until end of turn. Scry 1.

End the Festivities

End the Festivities deals 1 damage to each opponent and each creature and planeswalker they control.

Antagonize

Target creature gets +4/+3 until end of turn.

Tome Shredder

Haste
{T}, Exile an instant or sorcery card from your graveyard: Put a +1/+1 counter on Tome Shredder.

Ardent Elementalist

When Ardent Elementalist enters, return target instant or sorcery card from your graveyard to your hand.

Strangle

Strangle deals 3 damage to target creature or planeswalker.

Mountain

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

Immolation

Enchant creature
Enchanted creature gets +2/-2.

Abandon the Post

Up to two target creatures can't block this turn.
Flashback {3}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Fit of Rage

Target creature gets +3/+3 and gains first strike until end of turn.

Livaan, Cultist of Tiamat

Whenever you cast a noncreature spell, target creature gets +X/+0 until end of turn, where X is that spell's mana value.
Choose a Background (You can have a Background as a second commander.)