Hardened Armor is a skill located in the Draconic Power (which can be found in the Dragonknight skill tree). Hardened Armor is a morph of Spiked Armor.
Hardened Armor deals the following types of damage: Magic Damage. Which means that it gets buffed by the following blue champion point trees: Bastion, Elemental Expert, Elf Born, Master at Arms, Spell Erosion. Also the following red champion point trees protect against this skill: Elemental Defender, Iron Clad.