Amaranth - Rank 1 in the House of X's leadership, a Mutant with a near-physically perfect body whose cells can be used to enhance the bodies (and thus mutations) of others, with lower usage of her cells simply granting enhanced abilities, healing factor, and statistics, and higher and higher usages making the victim more and more like her, with the highest usage turning them into a mental and physical copy of her with slightly weaker attributes than Amaranth Prime, but retaining any mutation they had beforehand. Mr. Sinister's second-youngest daughter, Amaranth always spent her time with Sage, having the best relationship with her out of all 7 sisters, becoming a near-inseparable duo. As such, when the HOX fell apart and Sinister let his daughters loose on the world, she decided to stay at Sage's side rather than go off and form her own enterprise or empire like her other sisters, becoming Sage's second in command. She (and any other fully converted instances of her) act as Sage's personal attendants and servants, being the ones who handle things in Sage's personal chamber complex in the HOX base at Mt. Fuji, with only select exceptions (such as Satsujinki) even being allowed to enter her chambers at a given time. In the control scheme of the House of X, her main role is to supply her cells, usually in the form of her blood, to weaker members to strengthen them if necessary, as well as sell it as a special drug, Kick, made to enhance Mutant abilities.

She has a very disturbing personality, always being filled with a level of chidlike, girly glee, and hardly ever even changing her attitude from this kind of fake cuteness, but she has an undeniable streak of sadism and cruelty to her, loving defeating her enemies as horribly as possible and getting excited whenever Satsujinki takes a prisoner to make them into a Lily. She believes that mutations are a gift from a higher power, and people should be free to use them however they like, not bound by law or morality. This isn't a one-dimensional philosophy however, as she respects and admires whenever her enemies agree with her philosophy, even if they seek to use their mutation for good. She should be able to infect people with herself or kill people with her great strength and speed as she likes - and her enemies should be able to heal people of her infection or try and stop her as she likes. It's no big deal to her, and she accepts the possibility of defeat - but only in a world where Mutants are free to use their powers however they like, whenever they like. She often goes on long winded, almost comical rants about how denying Mutants their ability to use their mutation freely is a human rights violation. As such, among the HOX she has possibly the best relationship with the BOM's members, due to their similar philosophies. She and Sublime get along in particular, often having long discussions together in their free time about the ideal world they want to make.

Despite being a Sinister, she makes emotional connections with other people extremely easily, and often compliments her allies AND enemies whenever she thinks their mutations or abilities are super cool. She also crushes extremely easily, albeit only on women, and has a crush on almost every female member of the X-students, and even a few of their teachers. In particular, she crushes hard on Double due to the similar maximum output effects of their powers, as well as their clashing color schemes (bright and colorful for Amaranth, black and white for Double). She's curious what kind of daughter they'd have together considering their similar X-genes. Despite her adoration for her older sister, she doesn't have any incestuous feelings for her and is quite offended whenever anybody thinks so or jokes about it, particular Xorn, both prone to butting heads with each other due to the polar opposites of their style and personalities. Since there are many instances of Amaranth in the HOX, many of them are in relationships with Marauders or other lesser HOX members, but Amaranth prime is single, and declares she's saving herself for Double after they first meet in the Caribbean Drug Ring arc. She also has a romantic obsession with Wither, considering her super cool, but knows they could never be together due to Wither's age in comparison and how Wither would kill her from her power if they were together, which can bypass healing factor.

Her goofy personality also leads her to get along extremely well with the Marauders, even if many of them are creeped out by how most instances of her they meet used to be different people. Nonetheless, as many of her instances are part of the Marauders, she gets along with them well, and her levity means she can make them feel more safe in a battle situation, providing much needed emotional support when competing with either heroes like the X-men or rival criminal alliances which haven't allied with the House of X, such as the Fisk Crime Ring or the Hand. Her cuteness and charming sides also make it so her enemies often let down their guard around her, especially X-Students, often leading them to fail in fights against her copies. There are exceptions to this - mostly the more rough members of the X-Students like Sunspot, Monet, Cyclops and Quinby. She loves fighting with people, enemy or ally, and considers it the most fun part of her job. She also likes being congratulated for a job well done, especially in the form of headpats from Sage. She hates failing, often prompting a usually never seen angry side, which constantly screams and yells in comical fashion, especially with her high pitch voice.

She wears a cute lolita dress primarily made of pastel shades of purple and pink, with a stitched X-themed burgundy lace near the neck, a white x-shaped choker on the neck, and prominent, thigh-high pastel purple boots with similar-patterned laces running up them, as well as dainty, pinkish purple gloves on her hands, with frilly cuffs at the end. She usually has a cute accessory on hand like an umbrella. Her hair is a rich burgundy color like an Amaranth flower, and is styled in a curling fashion designed to be rather cute, with a white bow on top. Individual lesser Amaranths might have different outfits and hairstyles. Her eyes are red-pink with glowing red pupils, as well as prominent, glowing red veins stretching across the iris from these pupils.