Unholy Heat is a mythic Instant card from Special Guests (SPG), collector number 71. Current market price: $1.47 (foil $8.49), TCGplayer market prices via Scryfall.
Unholy Heat deals 2 damage to target creature or planeswalker. Delirium — Unholy Heat deals 6 damage instead if there are four or more card types among cards in your graveyard.