Burning Inquiry

Each player draws three cards, then discards three cards at random.

Mana Clash

You and target opponent each flip a coin. Mana Clash deals 1 damage to each player whose coin comes up tails. Repeat this process until both players' coins come up heads on the same flip.

Brass's Bounty

For each land you control, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Volcanic Vision

Return target instant or sorcery card from your graveyard to your hand. Volcanic Vision deals damage equal to that card's mana value to each creature your opponents control. Exile Volcanic Vision.

Hit the Mother Lode

Discover 10. If the discovered card's mana value is less than 10, create a number of tapped Treasure tokens equal to the difference. (To discover 10, exile cards from the top of your library until you exile a nonland card with mana value 10 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)

Flame Wave

Flame Wave deals 4 damage to target player or planeswalker and each creature that player or that planeswalker's controller controls.

Reckless Endeavor

Roll two d12 and choose one result. Reckless Endeavor deals damage equal to that result to each creature. Then create a number of Treasure tokens equal to the other result.

Spite of Mogis

Spite of Mogis deals damage to target creature equal to the number of instant and sorcery cards in your graveyard. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Apex of Power

Exile the top seven cards of your library. Until end of turn, you may cast spells from among them.
If this spell was cast from your hand, add ten mana of any one color.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Krark, the Thumbless

Whenever you cast an instant or sorcery spell, flip a coin. If you lose the flip, return that spell to its owner's hand. If you win the flip, copy that spell, and you may choose new targets for the copy.
Partner (You can have two commanders if both have partner.)

Immolating Gyre

Immolating Gyre deals X damage to each creature and planeswalker you don't control, where X is the number of instant and sorcery cards in your graveyard.

Dance with Calamity

Shuffle your library. As many times as you choose, you may exile the top card of your library. If the total mana value of the cards exiled this way is 13 or less, you may cast any number of spells from among those cards without paying their mana costs.

Sundering Stroke

Sundering Stroke deals 7 damage divided as you choose among one, two, or three targets. If at least seven red mana was spent to cast this spell, instead Sundering Stroke deals 7 damage to each of those permanents and/or players.