Muraki really really needs to kill or injure SOMEBODY. Once the hallucinations kick in he will be angry and violent. He can outright attack your character, but keep in mind that he is not an especially good fighter and I don't have any plans for him to be killed personally. That said, he has the anatomical knowledge to kill effectively and quickly, or, if you prefer, drug and torture you maybe??? Alternatively, he's manipulative enough to maybe trick your character into a hazardous situation and kill them that way (long shove off a catwalk, into the meat grinder, out the airlock, etc....)