Mammoth also known as "Mammoth The Mad", "Edward Windmere" and "Mammoth The Prideful" is the Sixth Lord of the Baator Realm as well as the Lord and Master of Malbolge The Plane of Envy.
He has extreme case of Obsessive–Compulsive Disorder or "OCPD" for short and extreme case of Schizophrenia. With both mixed together it made mad with the idea of wanting everything around him, to be made perfect as he wants it to be. For example, he is willing to completely destroy then rebuild, an massive capital city if he found even the slightest flaw in how it looks in his twisted mind.
Well taking an appearance of a Human Form, he is a depicted as a male human in his mid 20's, has short hair, a normal male build, as well as a long jacket with matching pants and a cane which turns into a long-sword after he twists the handle and taps it on the ground.
In his Archdevil Form he is shown to be a much larger built figure with a monstrous humanoid face and skin. He shown to have black vines along his body as he trying his best to become the "Perfect" looking being as such he tries doing magic and various kinds of transformations to alternately change his appearance to hide his true form.
In his Monster Form as a last resort, Mammoth returns to his original form, this form is a large massive fiend has the lower body of a brown-spotted serpent and the upper body of a muscular humanoid with two powerful arms. The creature’s bestial head is terrifically monstrous, with a black-lipped maw filled with pointed teeth and a pair of serpent’s fangs. His eyes are pale white, without irises or pupils, yet he seems to see perfectly. He hates using his form since in many ways, he believe this form is far from perfect in fact it the that he thinks of it as a freakish abomination of a body compared for his "Perfect" mind.
Among all the Archdevils ruling the 9 hells none are more crazy or distrustful then Mammoth. He is force to be reckon with he has one major flaw that psychologically tortures him as well as physically handicapping him on occasions suffers that of which has become a character quirk of his obsessive-compulsive personality disorder, or OCPD, which is manifested as an obsession over perfection.
Thus if anything is wrong by any measurement (a picture frame crooked, or not folding his toilet paper, for example), he will try to correct it right away, even at the expense of the mission or sometimes even battle at hand. He is so obsessed with symmetry however, he also suffers from a case of Schizophrenia, an mental illness which is a mental disorder often characterized by abnormal social behavior and failure to recognize what is real. Common symptoms, being unclear or confused thinking, auditory hallucinations, reduced social engagement and emotional expression, and sometimes even inactivity.
This makes him a unpredictable foe since he can be both an ally and a enemy depending on his mind mentally thinks of how you act and dress could depend on if you live or die. As well as he is a master of the black arts of magic he spends his time reading books and trying to find a way to become utterly "Perfect" instead of what he is underneath the skin. Those who service under him for years found ways to stay on his good side, however those who he just met for the first time might have a more of a tougher time earning his favor then the other Arch-devil Lords.