Runaway Steam-Kin

Whenever you cast a red spell, if Runaway Steam-Kin has fewer than three +1/+1 counters on it, put a +1/+1 counter on Runaway Steam-Kin.
Remove three +1/+1 counters from Runaway Steam-Kin: Add {R}{R}{R}.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Mountain

Gamble

Search your library for a card, put that card into your hand, discard a card at random, then shuffle.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Seething Song

Iron Myr

Arcbond

Choose target creature. Whenever that creature is dealt damage this turn, it deals that much damage to each other creature and each player.

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.

Big Score

As an additional cost to cast this spell, discard a card.
Draw two cards and create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Call Forth the Tempest

Cascade, cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom of your library in a random order. Then do it again.)
Call Forth the Tempest deals damage to each creature your opponents control equal to the total mana value of other spells you've cast this turn.

Demand Answers

As an additional cost to cast this spell, sacrifice an artifact or discard a card.
Draw two cards.

Thran Dynamo

Star of Extinction

Destroy target land. Star of Extinction deals 20 damage to each creature and each planeswalker.