Damage Threshold

Damage Threshold is a concept from the DMG I don't remember seeing used often in UA or homebrew content. Modifying it slightly, lightning damage threshold only applies to lightning damage. I think it would be interesting to apply it not just to objects, but for use in spells, magical items and class abilities.

Below is the definition from the DMG. I would infer from it that resistances and other modifiers are applied to incoming damage before determining if they surpass a damage threshold.

Damage Threshold. Big objects such as castle walls often have extra resilience represented by a damage threshold. An object with a damage threshold has immunity to all damage unless it takes an amount of damage from a single attack or effect equal to or greater than its damage threshold, in which case it takes damage as normal. Any damage that fails to meet or exceed the object's damage threshold is considered superficial and doesn't reduce the object's hit points.