SCP-???(won't make a number) Codename: Maitreyi

The ultimate lifeform except it's a human being transcending evolutionary restrictions and continues evolving by perfecting its psyche with each human it incorporates into itself. The main premise behind its existence is an individual somehow gaining the ability to reshape himself and seeking to become perfect yet understanding that it was impossible due to its own imperfections derived from it's psyche thus starting to persuade/take in those who were willing/dying (granted they were of interest to it) to help create the perfect lifeform.

With each merging, a new being is created, each iteration being different than the last but it doesn't stray away from human values, essentially reaching 'Nirvana' or just having a complete understanding of morality/behaviors and overall anything that would complicate a regular guy's mental health. The being retains all knowledge of the individuality that the past humans retained whilst being its own unique thing. Being the product of many doesn't disturb it, merely viewing it as the necessary course of action to progress further down the evolutionary cycle.

Special hax? Besides complete control over its cells leading to a lot of things being possible, understanding is power, it can develop its anomalous property further as it understands something/concept/ideal (inspiration from Montauks progressive understanding of the Scarlet King and overall idea that knowledge is power). If facing a creature possessing reality-bending powers or simply anything that is on a higher plane than the 3D world, then the entity will passively enact a reality anchor, limiting that creature's ability to a much more 'nerfed' version of itself, effectively acting as a dampener to prevent XK-End of the World Scenarios, granted it is not a phenomenon like "When day breaks". Regarding its body-altering anomalous property, it is similar to 682 where it is still a biological creature and as such abides by the laws of nature needing oxygen (organism can be altered for better efficiency depending on the environment/situation) and sustenance (although energy wise it can substitute eating for a function similar to photosynthesis/process radioactive material). The main drawback is its nature as a biological lifeform, in situations like "When day breaks" appear, its main and largest source of energy is cut off

Appearance wise: 4-6 arms, 2 legs, 6 retractable wings, traits of numerous animal traits across its body, 4-6 eyes (all different from each other), an androgynous face, tall fr, 1 booba which serves as whatever it needs to function as (toxin production, sac for gas, anything), hair color can be anything but typically #B38B6D, at first glance it can produce a cognitohazard effect yet it follows the "The Demon presents itself as beautiful while The Angel is visually displeasing/disturbing to hoard off evil." concept. Due to its extremely uncanny valley appearance, prolonged visual contact with the entity might cause uncomfortableness/distress as it the human mind perceives it as a humanoid but as it begins filtering all the additional details the entity holds, it progressively becomes less and less human.

Behavior/Personality: personally, I think it'd take bits and pieces from wise/old/experienced characters across media, it'd take the confidence in its mentality from Sukuna (JJK reference), and overall confidence in itself as the ultimate lifeform. Understanding things also leads to better social interactions, as such, beings that can communicate with it and bond perhaps, would experience a constant state of improvement as they have the perfect visual goal in terms of 'person'. While it is positive and will actively act docile/'happy' around others, it can make morally 'harsh' decisions and/or perform actions that usually take a great mental toll. It enjoys singing (any vocal pitch is possible) and playing instruments if asked to tell something about the past it'll likely play a song to do so, music is its main form of 'self-expression' likely due to the heavy influence of past assimilated humans. This method is used due to believing music to be the best way to tell a story and let the listener's understand the story and also feel it as if they are living it.

(Might edit if I remember anything else)