Murder Rat had hands and feet with three-foot-long machete blades attached to them. Her eyes were small but surprisingly human, and nearly buried behind her altered face and brow, which had been altered into something that was more rat-like than human - conelike, ending in a squashed black nose that had staples around it. Bonesaw had added a second set of teeth, all canines, so that the woman would have enough as her jaw was stretched forward. Drool constantly leaked between her teeth in loops and tendrils. She had long, greasy hair.
Her body was "emaciated". She was pale, except for her face and patches all down her body, where patches of ebon black skin were stapled in place.
Although seemingly a single woman, Bonesaw had combined parts of Mouse Protector and Ravager, using transfusions of bone marrow and viruses with modified DNA inside them until even Panacea couldn’t tell for sure where one woman started and the other began. She had one and a half brains contained in a synthetic fluid in her skull.
There was a metal framework throughout her body, controlling her, rigged to kill her with needles surrounding her heart if it was ever disabled.
The later clones of Murder Rat boasted enhanced senses, and were not held together with staples.
When she cut someone with her blades, the wounds would begin fizzing and emitting smoke that stung eyes; they took a long time to heal, and almost always left a scar. Left untreated, they would usually bleed out. The effect was more intense when she was close by. The venom continued to widen the wounds she inflicted for some time even after her death.
She was able to "tag" something or someone by scratching them using Ravager's ability to sense people she injured and Mouse Protector's power to teleport to those she had touched, although the blooming smoke made it more obvious who she was teleporting to.
When Grue copied the powers of a trio of Murder Rats, he mentioned that he could "kind of sense what others are sensing around me".
Her skin was "as tough as leather" and highly resistant to Taylor's bugs, and she had some kind of enhanced strength, flexibility, reflexes and agility. They were able to cling to surfaces with their claws.
An artificial member of the Slaughterhouse Nine, courtesy of Bonesaw. Murder Rat was a member in full having passed the requisite examinations. Yet over time the horror would slowly fall apart and lose the brains and skills that had made her such a terrifying presence. In the end she was just a rapidly putrefying corpse being used as a lackey.
↑ 2.02.1I set my bugs on her. She persisted, simply enduring what they were doing to her. I tried to go for the tiny eyes that were nearly buried behind her altered face and brow, but she shut them, relying on touch and smell to move. I started to pack bugs around her nose and mouth, and found that slowed her just a fraction. - Excerpt from Sting 26.3
↑Her mouth, conical, shaped by surgery into the vague shape of a rat's snout, riddled with canines, lowered towards his face. Her eyes are so human. I wouldn't have thought. - Interlude 26b
↑ 5.05.15.2I was aware of a Murder Rat popping in on the ground floor, crawling on hands and feet that each had excessively long blades on the ends. She moved faster than she should have been able to, considering her means of locomotion, but she had an exceedingly strong, flexible body. Enhanced senses, too, with her conical nose close to the ground, long greasy hair brushing against the surface. I almost turned back to deal with her, but she was already gone, moving faster than my bugs could. - Excerpt from Sting 26.3
↑"Murder Rat, she's on the top-" She pushed herself free of the vent, lunging, drawing her claws together as if she were diving into water from a height. Her narrow, emaciated body slipped right between the railings of the ascending and descending stairs. - Excerpt from Sting 26.3
↑ 7.07.1Murder Rat. Not stapled together as the original had been. She’d taken the time to do it well. When membership had been down, Bonesaw had made Murder Rat as a created addition to the Slaughterhouse Nine. She’d passed the tests, but degradation in mental and physical faculties over time had seen to her demotion. - Excerpt from Interlude 25
↑ 8.08.18.2She was a composite of two ‘kitchen sink’ capes. Mouse Protector and Ravager. Two primary powers that had blended into the one, a dozen other minor powers. Flexibility, a bizarre kind of enhanced strength, reflexes and agility that had peaks and valleys, and skin as tough as leather. - Excerpt from Sting 26.3
↑ 9.09.1Three Mannequins, three Murder Rats, three Breeds, a Nyx and a Tyrant taken out of action.
[...] Minimal casualties. A few injuries – Vista and Crucible would be out of commission as Murder Rat's venom continued to widen their wounds, and Golem was being treated for a burn. - Interlude 26 (Donation Bonus 1)
↑Ravager - Enhanced physique, all wounds inflicted would fester and scar horrifically if not tended to, scratches becoming eviscerations; maintained clairvoyant awareness of wounded.
Mouse Protector - Could teleport to tagged people or objects. Had lesser powers including increased coordination and agility
Murder Rat - Hybrid of Mouse Protector & Ravager. Agile, flexible, knife-fingers, wounds inflicted scar badly, smoke. Can teleport to side of any wounded. Slaughterhouse 9 - Parahuman List, bolded edits by Wildbow.
↑“Murder Rat,” Grue said. “Three of her. I can… kind of sense what others are sensing around me, and there's a glimmer of something that might be a teleportation power. I don't trust myself to use it without any ability to sense where I'm going." - Excerpt from Sting 26.3
↑An air vent at the very top floor was punched free of the wall. My bugs could sense the long claws, the conical nose. They started chewing on her, devouring and biting, but her skin was tough, as though most of it was scar tissue. - Excerpt from Sting 26.3