Board Thread:Warhammer 40k General Discussion/@comment-5846164-20121212083132/@comment-3580035-20121214104324

"She concentrated on the solidifying apparition, chanelling the energy stream that allowed her to pierce the veils of the Warp. Here, in real space, that stream erupted as a scourging beam of black light that struck the beast..."

There is a quote from The Lion short story from The Primarchs book. There other instances where it is used to 'blast' and 'blaze away' at enemies, and is also described as a "beam of darkness" later on. Also, at when the beam was being used, the First Captain of the Dark Angels had to avert his eyes from the Navigator's third eye, although he could watch the actual beam travelling towards the Greater Daemon.