Erinyes is a Force affinity epic from the Demonspawn faction. Erinyes is a mid tier epic with the ability to apply poisons and to extend the duration of all debuffs on targets. She also has a block buffs single target ability.
The best use for Erinyes is to utilise her as part of the Rhazin Scarhide legendary champion fusion.
You can actually fuse Erinyes from 4 rares to do this, the rares being Wanderer, Valerie, Gnarlhorn and Raider.