Unholy Heat is a common Instant card from Modern Horizons 2 Timeshifts (H2R), collector number 13. Current market price: $0.58 (foil $0.35), 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.