Piercing Additional Damage

Piercing Additional Damage (often referred to as "%HP DoT" or "Piercing DoT") is an effect that deals damage to afflicted enemies at the end of the turn. Unlike the original counterpart of Additional Damage, Piercing Additional Damage ignores all mitigation buffs that can reduce DoT damage and deals damage equal to a portion of an enemy’s max HP similar to Proportional Damage.

This effect is most common on skills of units with the following Elemental Synergies: Blaze, Tsunami, Tremor, Plasma, Aurora, and Abyss

Interactions with Gradual Healing
This effect will always occur before Gradual Healing takes effect, making it a common strategy and a necessity to use Gradual Healing to counter Additional Damage.

Interactions with Turn’s End to Start Effects
Unlike Gradual Healing and Gradual BB Gauge Boost, Additional Damage will always occur at the end of the turn and cannot be manipulated by any means. It is highly advised to not use Turn’s End to Start effects, as units will become highly vulnerable without utilizing Gradual Healing to survive the incoming attacks on the following turn.

Interactions with Shields
Shields take damage from Additional Damage rather than the unit's HP. Should the shield wear off as a result of Additional Damage, the remaining damage

Formula
DoT = [(UnbuffedATK x (DoT% + 100)/100) - (TotalEnemyDEF/3)] * Element Mod /100

UnbuffedATK = Base ATK + DoT Flat ATK + Imp ATK

TotalEnemyDEF = Enemy DEF after all buffs

Element Mod = 1.5 if strong element, 0.5 if resisted element, 1.0 otherwise (unaffected by EWD)