Its a aura-mod that ''can'' spawn on bosses/mobs.
-Aura Enchanted
-Cold Enchanted
-Cursed
-Extra Fast
-Extra Strong
-Fire Enchanted
-Lightning Enchanted
-Magic Resistant
-Mana Burn
-Multi-Shot
-Spectral Hit
-Stone Skin
-Teleporting

Lichking or Diablo from time rift wont spawn with Conviction aura tho
But its possible some bosses have -piercing res, if so @Game knows the numbers tho!