When king Engra summoned deamons of the Void to the real world, he realised they are highly unstable without constant source of life energy to consume. So, in blasphemous ritual he sacrificed his knights so they've became hosts for deamons. Void Warriors. They shared all combat adventages of deamons, in addition to ability to feed of their own pain and fury. As Void deamons are blind, sensing magical field and energy of life, Void Warriors wear fully enclosed helmets to show their bond with the Void.