Blighted gear can be looted of WA (Withered Aegis) monsters or be player made. There are blighted jewelry, blighted weapons, blighted claws and blighted scales.
These blighted items can increase your skills a lot, way more than regular non-blighted gear. But blighted gear can also decrease your skills, so be sure to watch what kind of blighted gear part you are equipping.
Blighted gear has a recharge value, this means that a blighted part can be depleted over time. You need to look at the item then what kind of item is needed to recharge the blighted part. To recharge it the use item. However, the item can only be recharged a couple of items and becomes unusable after.