Question: what are nethershards used for?
Answer: Nethershard is a currency used to purchase items sold by the Captive Wyrmtongue at Illidari camps in Stormwind, Orgrimmar, and Legion Invasion sites, as well as several vendors on the Broken Shore. Specifically, they are crystalized fragments of residual nether energy, a solidified form of the Twisting Nether itself.