Murderface has brown hair, lime green eyes, a heavy lateral lisp and a diastema, as well as tattoos on his stomach which state "Pobody's Nerfect" and "This Mess Is A Place." This is also a reference to Kirk Hammett's tattoos as he also has a tattoo on his stomach in that design. He is overweight, stocky, hairy, and repeatedly referred to as 'dog-faced' and 'pug-nosed' And is The Bass Player for Dethklok.

William is incredibly sensitive about his appearance, which his bandmates show little sympathy for and frequently contribute to with disparaging and vituperative remarks. His face looks like murder, hence his namesake. He hinted that his grotesque looks may have been a motivating factor in his parents' murder- .

Dr. Gibbitz, the Tribunal Murderface expert, describes Murderface as being the "perfect specimen of devolution", with a "Cro-Magnan brow, distended jaw, clammy hands, puckled stomach, back pimpleage, hitchhiker thumbs, hammer ass, fallen arches, chicken-plucked legs, sandpapery eczema-style skin, and dry, unkempt triangle hair".

Murderface's use of his to play the bass has reportedly left it callused, giving it a "gnarled" appearance as if it had been 'stuck in a hornets' nest', according to Pickles the drummer. Pickles The Drummer and Skwisgaar Skwigelf also described his backside as looking like cottage cheese, with razor-burn and stubble.

He is usually seen carrying a knife, which he uses to eat, mutilate, destroy, and do other things. Murderface has a habit of urinating inappropriately (on a display of olives at the grocery store and on journalist Nick Ibsen's shoes) or referring to urination, and even has a one-man side project called Planet Piss, to which he seems to have very little real commitment.

He is quite homophobic, which becomes a sort of running gag with him, as he is often put in situations where it comes close to suggesting homosexual desires. He also refuses to eat anything he considers phallic, even if it is cut into small pieces. However, he is caught later eating a sausage, and His distrust of doctors is mainly due to his homophobia and his misunderstanding of medical examinations of the male genitals (comparing it to being "jacked off"). All of this behavior has led to fan theories that he is a self-hating closeted man.

he admits he has a habit of choking himself while jacking off every morning, and is very aware of his laziness.