Natural Invulnerable Armor
From AmtWiki
Natural Invulnerable Armor
A Type of Armor
Discription from the Dor Un Avathar
must be Mended instead of Heal, but otherwise has the abilitiesof both Natural and Invulnerable type armors. Monsters with a Heal Trait (such as Ice Heal or Stone Heal) can regain their Natural Invulnerable armor at the rate of one point per sectional location per use of their ability. (ex.: it would take three Mends to heal a wounded Gargoyle and restore both points of its armor to a single leg.)
