Spark Vulnerability is a debuff on the enemy that amplifies the amount of Spark damage taken.
Much like status ailments, Spark Vulnerability can be inflicted on enemies at a set probability for a set amount of turns. Once afflicted, the debuff cannot be cleansed by any means and will continue to take effect until the debuff wears off after a set amount of turns.
Interactions with other Spark Buffs
Spark Vulnerability will always stack additively with other spark buffs.
As such, a 150% Spark buff along with an enemy inflicted with 30% Spark vulnerability will result in a total Spark bonus of 180% added to the base.
Spark Vulnerability debuffs work similarly as status ailments in terms of how they are applied. As such, enemies will only be debuffed with the effect if their HP has not already reached 0. Any subsequent frames after the enemy's HP reaches 0 will prevent any status ailments or debuffs from applying.