From SoDWiki

Magic Damage is applied to the Listed DMG of your Weapon, 13 DMG 22 Delay, +2 Magic DMG = 15 DMG 22 Delay.
Magic DMG is Mitigated by Sv Magic as opposed to AC.

Magic DMG also affects Magic Based spells, adding all your +Magic DMG to the total damage done by your DD or DoT.

Related items

This article contains a list or table which is known or strongly suspected to be incomplete (likely due to the item reformatting project).