My MOGAI headcanons for Brook from the webcomic I'm The Grim Reaper because all the requests blogs were busy. Flags from left to right are: aroace, contreogender, muphridian, duragenderless, genderunique, aporagender, mogaihypic, cloudgender, rabbitgender, vulturehoarder, mortugender, lykh, corpsegender, bloodgender, zanggender, tentiagender, gendersanghe.
Definitions and reasoning under the cut!
Contreogender: A gender for someone who (generally speaking) believes society's attitude surrounding gender/gender roles is harmful and believes gender should not be so important. This belief leads them to not pay much attention to their own gender/only share their gender if absolutely necessary/only tell close friends about their gender. [Listen. Listen. Brook is over a century old. You think he gives a fuck about gender roles? At some point in time he probably had long hair, and there were probably a few people who assumed he was a woman, at which he probably realized that Gender Isn't Real.]
Muphridian: being man/masc-aligned, AGIN-aligned, and xeno-aligned. [Sums up his experience with gender pretty nicely. He doesn't really care about it, but he was born a man so he feels some connection to it, but his experience is beyond society's traditional understanding of gender.]
Duragenderless: when your gender is always partially agender. [As I said, Brook doesn't care that much about gender. In a way, this makes any gender he experiences sort of muted by his apathy. He perceives this as a small dose of genderlessness.]
Genderunique: a very personal, unique and interpretative gender that cannot be described using existing terminology. [Exactly what it says on the tin. Brook is so old and has been through so much that at this point they're probably the only person on Earth with their particular experience of gender. They sort of shrug it off when asked if they're a man or a woman, and says "I'm a reaper" or "I'm me".]
Aporagender: a strongly gendered feeling that is not male, female, or inbetween. [This kinda goes hand in hand with Brook's genderuniqueness. Not male, not female, something other and entirely separate. May or may not be related to the disconnect they feel from humanity as a whole.]
Mogaihypic: when your gender is affected by your hyperfixation on MOGAI. [Hear me out... what if Brook had ADHD? As anyone with ADHD will tell you, boredom is excruciating. It's even worse when you're immortal and have nothing but time on your hands. Brook hyperfixates on gender and hyperfixates on it hard, to the point that they hoard labels and probably run a (not very popular) MOGAI blog.]
Cloudgender: a gender which can’t be fully realized or seen clearly due to depersonalization/ derealization disorder. this gender is only for the use of neurodivergent people. [I headcanon Brook as having some sort of dissociative disorder due to trauma and the fact that she's over a century old, a timespan the human brain isn't really built to comprehend. Her dissociation makes it difficult to introspect and leaves gaps in her memory, which affects her view of herself and by extension, her gender.]
Rabbitgender: a subset of bungender for when one feels their connection to bunnies is not soft or cute, but rather feral, skittish, and territorial. [Need I explain? Brook feels a deep connection to rabbits because they're her demon, the thing she's spent decades caging and training and restraining, the thing she knows better than she knows herself. Of course she doesn't view them as anything resembling soft; how could she?]
Vulturehoarder: when you hoard AGIN and death-related genders. [Brook is dead. Xe's dead. It affects every part of xyr life; why not xyr gender? As this is pretty much the reasoning behind every gender after this, I won't be expanding further on those.]
Mortugender: a gender / gender addition that has strong ties to or relates to death in a deep way. The prefix mortu- is added to a gender when said gender becomes stronger in the presence or feeling of death. Coined with people with Cotard’s Syndrome in mind, but isn’t exclusive.
Lykh: A xenogender characterized by supernatural vigor and a sense of disembodiment. Someone who identifies as a lykh might feel like their gender exists in spite of or apart from their earthly existence. Synesthetically, this gender feels undead, incorporeal and/or extradimensional, like a conspicuous absence.
Corpsegender: A xenogender / kingender relating to one’s undeath. One’s gender perception is altered by the fact that they are undead, their gender might be muddled or weak but not necessarily. Some examples of “undead” can be zombies, vampires, ghosts, etc.
Bloodgender: A gender that is shrouded in confusion because of an overwhelming feeling of animalistic rage and feralness. This gender has a lot to do with frenzied confusion, anger, and visuals of gore and violence.
Zanggender: A gender based off or related to the "zannie" unnatural (Kovit in particular) from the book series Market of Monsters by Rebecca Schaeffer (or the Webtoon adaption 'Not Even Bones'), and/or a gender that draws energy from others' pain/violence. May or may not feel malevolent and/or related to blood. From the French word 'sang', meaning blood.
Tentiagender: A gender based off of or related to Nita's (main character of Market of Monsters by Rebecca Schaeffer) ability to control bodily functions, and/or a gender that feels made of many parts, each of which can be controlled through concentration, but is draining to control. From the Latin word 'potentia', meaning power/force.
Gendersanghe: a gender that feels thick, sometimes dangerous, iron-like, and related to blood. It can be connected to winter, darkness, and death.
I also headcanon xem as sepulcherine/ morguegender but I couldn't find a flag for that!