Taar

Taar is nuclear mutant created by a combination of chemical and toxic waste both human as extraterrestrial dumped in one of the tar pits of La Brea. Blight give him birth by a nuclear blast and used against Ben and the Gang. He wasn't created to kill them, only to keep them busy and as a warning to prove he's still alive. He appears in Perfection has no age in Ben 10: Alien Alliance.

Description
Taar is a dark red-purple monster made of tar and bones, the bones of the creatures that have died over the years in the pit. His skull is that of a smilodon, proving is large fangs. He also have mammoth-tusks. His arms are different from each other: his left arm is made of the spinal cord and skull of a prehistoric carnivore of unknown origin. His right arm is made of another spinal cord as he has a stegosaur's thagomizer instead of a hand. The spinal cord are protected by thick tar. His ribs are visible and just as the tusks, they belonged to a unfortune mammoth. His true spinal cord is also very visible through the tar. In his lower body we see he have two little feet. They are possible from the same carnivore as the head of his left arm.

Taar is mindless creature as described by Ben and lives on pure instinct. The only reason why he attacked the villagers close to the tar pit was because he was hungry. The same reason why he attacked Ben and the Gang.

Origins
Several million years ago, animals have disappeared and drowned in the tar pits of La Brea. Some alien maffiosa thought it would be no problem to dump very toxic waste in it. It was illegal stuff and very expensive to destroy it properly. And since there is nothing that lives in the tar, no one should complain. The problem is, some men thought the same. They dumped the toxic waste of their factory in the tar pit, believing it was harmless. Blight discovered this and kidnapped several men of the factory, including the CEO and his secretary. He wanted to do some tests. First he drops his secretary in the tar pit. Few minutes later she was completely gone. Blight was amused by the effect and decided to test what happens with the tar if he enrich the pit with some of his nuclear energy. He created a creature called Taar. The beast immediatly attacked the men and eated them all. The CEO tried to escape but was stopped by Blight. He grabbed the man, burned his face and throw him right in the mouth of the beast.