Long-Forgotten Gohei

Arcane spells you cast cost {1} less to cast.
Spirit creatures you control get +1/+1.

Overblaze

Each time target permanent would deal damage to a permanent or player this turn, it deals double that damage to that permanent or player instead.
Splice onto Arcane {2}{R}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Glacial Ray

Glacial Ray deals 2 damage to any target.
Splice onto Arcane {1}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Skyfire Kirin

Flying
Whenever you cast a Spirit or Arcane spell, you may gain control of target creature with that spell's mana value until end of turn.

Ornate Kanzashi

{2}, {T}: Target opponent exiles the top card of their library. You may play that card this turn.

Ire of Kaminari

Ire of Kaminari deals damage to any target equal to the number of Arcane cards in your graveyard.

Jiwari, the Earth Aflame

{X}{R}, {T}: Jiwari, the Earth Aflame deals X damage to target creature without flying.
Channel — {X}{R}{R}{R}, Discard Jiwari: Jiwari deals X damage to each creature without flying.

Azamuki, Treachery Incarnate

Remove a ki counter from Azamuki, Treachery Incarnate: Gain control of target creature until end of turn.

Cunning Bandit

Whenever you cast a Spirit or Arcane spell, you may put a ki counter on Cunning Bandit.
At the beginning of the end step, if there are two or more ki counters on Cunning Bandit, you may flip it.

Cunning Bandit // Azamuki, Treachery Incarnate

Blind with Anger

Untap target nonlegendary creature and gain control of it until end of turn. That creature gains haste until end of turn.

Shimatsu the Bloodcloaked

As Shimatsu the Bloodcloaked enters, sacrifice any number of permanents. Shimatsu enters with that many +1/+1 counters on it.

Scorched Rusalka

{R}, Sacrifice a creature: Scorched Rusalka deals 1 damage to target player or planeswalker.

Ghost-Lit Raider

{2}{R}, {T}: Ghost-Lit Raider deals 2 damage to target creature.
Channel — {3}{R}, Discard Ghost-Lit Raider: It deals 4 damage to target creature.

Glitterfang

Haste
At the beginning of the end step, return Glitterfang to its owner's hand.

Mountain

First Volley

First Volley deals 1 damage to target creature and 1 damage to that creature's controller.