Blighted Aspect is a Necromancer Offensive Aspect that can be found by completing the Akkhan's Grasp Dungeon as well as from random enemy drops. After clearing the Dungeon for the first time the Aspect will be available in your Codex of Power.
How to Obtain - Codex of Power - Akkhan's Grasp
Blighted Aspect Mechanics
Legendary Aspects can change the way skills and builds work in significant ways.
For further information, see our Build Guides, Legendary Aspects & Codex of Power
Blighted Aspect