Damage Taken From Mana Before Health is a defensive mechanic primarily available for Mages, which is mostly obtained through items. Sorcerers, a mastery specialization for Mages, also have this stat available in their passive trees.

When a character has any % of Damage Taken From Mana Before Health, a portion of the damage will be dealt to their mana instead of health. However, if they are at 0 or negative mana, then all damage is applied to health instead. Damage Taken From Mana Before Health stat does not protect ward, similar to endurance.

Having more than 100% Damage Taken From Mana Before Health does not have any additional effect.

1 Point of mana shields 5 points of health. For example, if a character has 90% of Damage Taken From Mana Before Health and takes 1000 damage after all other reductions to damage taken from other defensive stats, such as armor and resistances have been applied: -100 Damage is dealt to health, as 10% of 1000 is 100.

-180 Damage is dealt to mana, as 90% of 1000 is 900, which is then reduced by dividing by 5, which results in 180. This means that effectively your mana has 80% damage reduction.