What does the "blessed armor" affix?

Just found a robe with this affix. I like the way it sounds, but what's the effect exactly ?

The answer's lying in one of their patch notes:

We’ve added depth and diversity to the hero items by introducing new item abilities. In the past, you may have found items with basic abilities such as a chance to Stun or Poison your target. Pack 18 introduces the following new abilities:
[...]
• Blessed Armor : The hero’s physical and magical armor is increased for a short duration
[...]
Your items have a chance to trigger one of its abilities any time you attack a creature.