Hi, this is Joy. Before we go to the story, I want to explain about this rare dynamic called Sigma. You rarely seen this in most omegaverse stories, not even as side characters. Below I will explain in bullet form, most explanation are from my own research in which are explained by others and mix of my own headcanons.
Please note that sigma is still new to most people in omegaverse, since they were only known for being archetype before this, so my explanations below of sigma headcanons are unofficial and it can be vary. After doing many research, some people have little differences in their sigma headcanons, so I will only collect those headcanons that are the same and add mine to suit the story.
[ also shout-out to user wild-world-of-omegaverse from tumblr, i used their sigma hcs alot because they have better enlightenment about sigma than others that i have read ]
• hierarchy : in most platforms you can see that sigma stands at the same level as alpha, or maybe higher than alpha. it is because of they have so many similiraties with alpha, that they were always mistaken as one. no one will know unless they're being told. sigmas are also known being alpha with 'lone wolf' personality. unlike alpha who stand for their status and like to lead their packs, sigma prefer to step out from the hierarchy and not follow the law of the hierarchy. they don't like to control or being controlled.
• appearance : they can differ and have the most diversity in body type, but, the most common body types usually fall into shorter but bigger build, or taller and smaller build. as for their canine expression they have lower canines that are incredibly sharp. (meanwhile alphas have sharp upper canines)
• strength : they are as strong as most alphas, are stronger when they have ruts
• pheromone : their pheromone can weaken the alphas, calming the betas & weaken/arouse omega. when they're annoyed/irritated, they naturally let out strong pheromone so they usually avoid crowd to not cause trouble for others
• scent : sigmas have spicier scents and there are times it can be too intense and potent especially during mood downfall.
• voice : the particular voice sigmas have differ from alphas because it release fear in alphas and release calming yet energizing hormones in betas, but has the same effect on omegas as alphas voice would have for them (omegas) which is arousal or dopamine in most situations.
• heat : sigma went through heat . unlike omega, sigma have no idea when their heat will come since their body don't usually act up before the heat week. when sigma is on heat, they're as weak as omega and they attract alphas, betas and even omegas to them. so when it is heat month they usually will stock up so many food, compile their favourite stuffs to their dens (nest for omegas). they'll disappear from the public to avoid any harm. sigma can die if they hold themselves from being mated for too long because the pain just getting worse everytime their heat come. their heat usually last for 4 days
• rut : sigma also went through rut. they usually have rut in a month then heat on the next month, and it continues on like that. during rut, their hormones are higher than alpha's, which make them stronger and crazily aggresive. unlike alpha who usually have rut when they are close to omega on heat, sigmas' ruts just like heat week. they also lock up themselves during rut time. during rut they release pheromone that can make any omegas near them want them so bad. the pheromone will take over the omegas' senses and they'll act as if they're in heat and in need of alphas. it is not impossible that they can activate omega's heat, but it's a very rare case.
• impregnate : sigmas can impregnate omegas and their children are most likely will be born omegas, but it's also possible to get baby sigma.
• pregnant : they can get pregnant if they're knotted by alphas, betas or omegas.most of the time their children will follow their non-sigma parent's gender, especially alpha and beta.
• mate : unlike alpha-omega, sigmas can be mated by more than a person. they can be mated and knotted by two people at the same time (there are scientific explanation about this but i can't remember and can't understand it since im not a science/bio student ;-; ). they usually give birth quicker than omega, which is three to five months. if they’re mated to an omega they’re more likely to have ruts more often than heats and more heats if mated to an alpha.
• social : although most sigmas are introverted, they're actually good at carrying conversation, only to those they trust/want.
• temperament : they are ready to fight whoever belittle them or their friends/loved ones even if they are against gang of dom alphas. their wrath can activate their ruts but it won't be as strong as those they naturally have, but it is more than enough to fight alone. they have habits of bringing various types of suppressants, repellent and other medications for themselves since they're very sensitive with many things and things usually occur during unexpected time for them.
additional points ;
• have a great intuition that can help them living on their own to avoid danger but make wise choices in social or educational situations.
• have the best eyes to look out for danger and for resources.
• sigmas have their own “sigma voice” unique to them .it sounds similar to a lion’s growl that releases fear hormones in alphas, happiness/dopamine in betas, and has a varied reaction in omegas that’s either fear or arousal depending on who they are.
• up to 90% are introverts making a social sigma rare altogether, but it isn’t impossible.
• sigmas are sometimes confused to be meek or shy when they have the typical quiet nature but anyone who thinks this and try to take advantage of it will learn real quick that they couldn’t be more wrong.
• sigmas are also rumored to be even better leader figure than alphas if they choose to take up the role as one, a rare thing, but still possible.
• when a sigma is involved with a pack it’s usually because the littermate they’re closest to or their own mate is in the pack or it’s just the entirety of this group is their familial pack.
• they’re the overseers and advisors who help to guide those around them and make sure the order of things is working out. because they’re the most affected by them after all.
• sigmas are the most impacted by other dynamic’s scents causing them to sometimes be very intense people, or loners depending on how well they can control themselves or how strong their scent diffuser meds are.
• if a sigma is mated to an omega, since sigmas are the most affected by pheromones, the increase in omega scents will cause them to get more ruts than heats causing their bodily strength to stay up than fluctuating like normal. vice versa if it's alpha-sigma mate
• since sigmas are the most affected by scents causing them to be very aware of their surroundings and have something similar to an omega’s memory. they can be very perceptive to the situation that they’re in and most will use it to their advantage if needed. which brings around the negative concept or rumor that sigmas are manipulative.
Please leave any questions below regarding sigmas, just in case I miss the important points/details here and there, I will edit and update this chapter to answer the questions! Have fun reading~