Nightkin are an elite warrior caste in the Master's super mutant army. Many of the Nightkin are equipped with cloaking devices, the Stealth Boys. A part of super mutant army which remained together after the death of Master forms a faction led by Attis and, many years later, captures the Secret Vault in order to use the FEV stored in it. Attis' goal is to continue the Master's plan. His army has an elite unit of Nightkins, which are much improved and use some new high-tec suits to advance their abilities. These suits probably originated and were made from Vault-Tec facilities in the region.