Board Thread:General Discussion/@comment-71.77.71.203-20151209032345/@comment-6881629-20151209094356

It's a set bonus, like Silver4Raven said wearing all for parts of Ahzidal's Armor will give you the bonus effect of plus ten to enchanting (all four parts or you don't get it). Deathbrand Armor is the one that does has a stack effect.