Monster GainsDamage Gained as extra XDamage gained as a specific damage type only scales with modifiers to the new type, not with modifiers to the source damage's type (unless they're the same type).
For example, Lightning damage gained from Physical damage scales with Lightning damage modifiers, but not Physical damage modifiers.
Damage Gain occurs in the same two step process as Damage Conversion. Damage over time cannot benefit from damage Gain. 40% of damage as extra ChaosChaos DamageChaos damage is one of the five Damage Types. It is reduced by Chaos Resistance.
Chaos damage is the least common damage type, and removes twice as much Energy Shield as the damage value when taken. damage.en