Proteus - Rank 2 in the House of X's leadership, and a Mutant with the Omega Level power of reality warping and an additional form of advanced, Non-Omega telepathic mind-transferral. Named Kate McTaggert-Xavier, she is the child of Cassandra Nova and Moira McTaggert, who was enslaved by her mentally for 3 years in the late 90s. She has an extremely warped and disturbing personality, due to a combination of her mother being Cassandra Nova, her other mother's subconscious negative emotions while she was in the womb, the level of power her mutation grants her, and how her body burns away and she needs to find a host after a certain amount of time depending on the body's resilience. She is extremely sadistic and loves using her powers freely to torture and horribly transfigure or kill other people, alter their perceptions, and overall ruin them. She is extremely childish and a small level of egotistical like her mother, to the point she always warps her host bodies with her powers to look like her original body if it were a teenager instead of burning away into nothing shortly after exiting the womb. She is somewhat lazy, preferring to rampage with her powers instead of participate in missions. This will only change if the mission personally interests her or Cassandra orders her to do it. She is extremely loyal to her mother, and will always obey her and is terrified of failing her and earing her disappointment, and seems to love her genuinely despite the horrible circumstances of how she had her. She also loves her birth mother, Moira, and can't comprehend why Moira doesn't want to be with her and Cassandra, always feeling depressed by the fact Moira is disgusted by her mere existence. Moira being present and against her is one of the only ways to stop her temporarily, as she refuses to hurt her.

However, Moira cannot stop her permanently as she will, as normal, just hop to a new body after once her current host either decays away or is killed. She loves weird interests such as Breakcore music, completely normal home videos of other people, those weird elsa games, and similar such things, highlighting her disturbed mind. She always wears a grey baggy semi-translucent raincoat, grey sweatpants bunched up a little under the knees, and blue kicks with tall, scrunched up socks, as well as t shirts that usually feature images that interest her, such as psychedelic visuals, anime-influenced pictures (often gory ones), and anatomaical references to humans and insects. She's pretty short, and has long, wavy, and messy white hair (which grays near the ends as her body decays), green-blue ESP and a cute, almost catlike face. As she decays, her body falls apart and more and more ESP-glowing cracks form all over it. Her eyes are normally gold like her mom, but as her body decays they become a more and more "cracked" and "scattered" glowing green-blue design.