The Hunger is the name given to the magic afflicting mental illness that the leakage of the Void through the Glitch has bred in the monsters of the Underground. It causes those afflicted to bleed tainted, clotted magic from their orifices, gives rise to unnatural and uncharacteristic aggression, and convinces its victims that they are starving constantly.
Under its influence, the monsters of the Underground quickly ate through all of their food reserves, and left with no other recourse, turned on each other for sustenance, slaughtering each other and consuming their own families and friends with little inhibition. The sickness only grows worse the longer the mists of the Void are allowed to spill into this world.
Only the strongest, both magically and mentally, can provide any resistance to the Hunger, and even then, it is limited. Humans would be less affected by it, as it is a magical sickness, but should they have prolonged exposure to its effects, or consume meat tainted by it, can and will suffer its effects as well.