Source: Yugipedia
Effect damage ((こう)()ダメージ Kōka Damēji), often colloquially referred to as burn damage, is damage inflicted by means other than battle. Examples of cards that cause effect damage are "Poison Mummy", "Ookazi", and "Ceasefire".

Not all means of decreasing LP are damage. Paying LP for a cost, card effects that cause a player to lose LP without using the word damage (such as "Soul Charge"), or changing a player's LP to a specific value (such as "Life Equalizer") are not damage.

While piercing battle damage is inflicted due to a card effect, it is battle damage rather than effect damage (as its name makes clear).

Some cards specifically counter or prevent effect damage, such as "Barrel Behind the Door" and "Des Wombat". "Prime Material Dragon" causes all effect damage to increase a player's LP by the same amount instead.

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