The Blighted Aspect is an Offensive Aspect. It can be imprinted on Gloves, Offhands, 1H Weapons, 2H Weapons, Rings and Amulets. It can only be used by Necromancers.
Effect
Consecutive hits with the Shadowblight Key Passive deal x[25 - 35]% increased damage for each hit, resetting after 6 seconds of the first.
How to get Blighted Aspect
The Blighted Aspect can be unlocked in your Codex from

The fastest way to get the Blighted Aspect is to gamble Offhands on a Necromancer.
The best way to get Aspects is to gamble your

