Doctor Challus Mercer (tʃɑːlʌs mɜrsɜr) was a scientist aboard the USG Ishimura and a devout Unitologist to the point of zealotry. Mercer became fanatically obsessed with the Necromorphs after the Ishimura was compromised and the infection spread; Mercer believed the Necromorph infection to be the next stage of the human race, and their ability to reanimate necrotic flesh was life after death.