From the preview:
Exposure to waves of raging Urghast energy causes horrific mutations and can turn people into pools of frothing flesh. Insane as it might seem to most, Banebrood shamans draw upon this energy and sculpt it to their design. Each breed of Beastspawn has its unique traits, and for the Bison-Brood it is their resilience to the warping power of the Urghast, which makes Bisotaurs ideal shamans.
Channelling raw Urghast power has long-term side-effects on the sanity and constitution of the shamans, and for this reason they carry devices called nightmare catchers – enchanted webs that siphon off the tainted corruption into Alchemyte crystals. Bisotaurs wear the shrunken heads of former enemies containing their enslaved spirits, bound to eternal service. These despairing victims perceive a few seconds into the future, and are compelled to scream when the shaman faces impending harm.