Demonic spawns. A grotesque-looking creatures without a mind of their own. They were like feral beast incapable of self-reflection or rationalization. Their very existence were sustained by instinct and the feeling of hunger for flesh.
These creatures were created as a result of the demonic energy that came out of the warp, the red spinning portal of which the demons used as a door to invade worlds. The demons were also contributing to the creation of these creatures as their aura spread. They let out these aura or some scents every time they breath, fight, or even die.
An unfortunate animals or humans would unknowingly absorb the aura and transformed into a demonic spawn that would kill anything it set its gaze upon.
As more creatures died, the demonic aura intensified to the point it got so powerful that even corpses could turn into demonic spawn.
That was the reason why there were tens of thousands demonic spawn currently charging at them.