It has been noted recently that in many of the early Xenos incursions into occupied areas of Ferron Proxima that amongst the hulking beasts and chittering hordes there was a being of immense psychic potential. This creature could be seen floating above it's smaller brethren, an eldritch light sparking from it's immense cranium and exposed synaptic cells. Unfortunately most field reports stopped there, as whatever witchery this creature held resulted in the decimation of whole ranks of heroic defenders of Ferron Proxima. One minute they were upholding the faith of the Emperor, the next minute they were but lifeless husks.
These two Tyranid bioforms formed an unlikely but effective symbiotic relationship, often with the pod being left ravaged by defenders eager to meet out some revenge for the horrific devastation the brain beast created. Quite often the brain beast would be left untouched by the blessed munitions of the Emperor, surviving hundreds of rounds of bolter shells and high energy weapon discharges while it feasted on the life-force of anything within reach. Many reports also suggested that despite this energy field and prodigious strength one crack shot in the right place would be enough to render all this psychic energy pointless as it' vaporised into the warp. Sadly though in the early days, for every confirmed kill there was another confirmed sighting. Once again reminding us that the Great Devourer is constantly evolving, mutating and gestating new horrors that must be destroyed for the Emperor and the safety of the Imperium.