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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.
The card types that can appear in a graveyard are artifact, creature, enchantment, instant, land, planeswalker, sorcery, and tribal. Legendary, basic, and snow are supertypes, not card types; Kavu and Equipment are subtypes, not card types.
Unholy Heat checks your graveyard as it resolves to determine if it deals 2 or 6 damage. At that time, Unholy Heat isn't in the graveyard yet.
