Probably after getting to nowhere, Herbert decide to see the effects of the Mortifilia in animals, more specific, in a frog, as they would be very accesible as he leave very closed to a river inhabited by them.
The infection of the Mortifilia radiccaly changed the frog:
It grew a lot in size, his whole body become a giant ball-like apperance, in this one there would be its eyes and a mouth with a great pair of external and internal teeth. Two horns grew out of what it can be consider its pelvis and his legs become a black-ish brown color, different from the light red-ish color of his torso/head.
It's seems that the frog biter escaped from the lab and made it to the surface, where it reproduce and made the first Tadpole and thus expanded the quantity of this kind.
Herbert decide to test the serum, made by the sample of blood of the Frog Biter, in a human being.
After infecting a student with it, he noticed as the time passed how he bassicaly became just the human torso subtented on the arms. It presents a mutation of type 3, in which the central nervous system is deleted and replaced by a hybrid nervous system.
During the mutation, the head is ignored in favor of other organs and is subsequently lost after a certain period due to the lack of blood supply. Not being, therefore, more able to stretch the muscles from the neck up, this kind of Biter has developed a kind of mouth from the rib cage, using the ribs as teeth.
Generally it attacks in groups of its kind or supported by stronger enemies using, however, any type of collective strategy.
The Biter has 3 known attacks:
Their primary attack is to make a headbutt to his enemy, is not as damaging as one could think, but it's quite helpful leaving time for the other biters to attack him.
Their more offensive attack is biting his victims in the legs as a dog would do. Even though it isn't so powerful, this is their strongest attack.
And their last attack is "spiting" a sort of slightly corrosive liquid in the direction of the enemy.
They are generally weak but very aggressive, the Biter is surrounded by a weak layer of dark spores that protects it from attacks, but with the application of light it's only need a few seconds to dissipate any defense, this will make it run away frightened.
A few hits of any melee weapon will slash this weak enemy or you can opt for the firearms and kill him with two or three bullets with the most weak gun. The light of a simple flashlight running low is enough to scare away this monster while the sunlight kills him in a few moments.