Warrior Istani armor

Description
The is an armor art used by all armor types in Nightfall Campaign  The Istani Helm with item's atribute +1 has recently been observed to retain the previous item's atribute bonus when changing a rune from one atribute to another. IE: Having a minor rune of Axe Mastery in place provides Axe Mastery +1 with a bonus of Axe mastery +1. Switching the rune to a rune of minor Strength changes the Istani helm to Strength +1, but retains the bonus of Axe mastery +1. It is not sure how this effects stacking with runes on on other areas of the armor.