Overblaze is a uncommon Instant — Arcane card from Betrayers of Kamigawa (BOK), collector number 114. Current market price: $0.33 (foil $4.99), TCGplayer market prices via Scryfall.
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.)