One of the main pillars of Skrellian society, the caste system has been in place for millennia on Qerr'Balak, its current form having stabilised around the 3rd millennium BCE. While the countless city-states of skrellkind display a number of variations around the model, most still follow the main structure established by their ancestors. However, new social structures are being adopted by colonies on the outskirts of Skrellian territories, particularly near the human border.
The caste model appeared as a solution to the growing Skrellian need for efficiency within their society. By immersing the Skrell in environments shaped to specific needs, goals and values, the castes were able to form generations of specialised Skrell whose skills and activities grew in harmony along their values and traditions. As such, castes act as subcultures within the main Skrellian culture, conditioning a Skrells life from birth to death and passing it along to their children.
A common mistake to make when considering the castes is their relation with professions. While their castes most certainly drive Skrell towards specific sectors of activity, the borders between them are tenuous at best and the same job can be undertaken by several castes with different emphasis and areas of specialty depending on the originating caste. A good example would be architecture: Kanin-Katish and Talum-Katish are both suitable for such an activity, the former with a strong focus on practicality and safety, while the latter would rather concentrate on aesthetics and cultural importance to the work. Management is also another example: While a speciality of the Qerr-Katish, it is not unheard of for Skrell from other castes assuming management positions after years of work in a specific sector (a researcher might, for example, gradually rise in status until being given responsibility of a research team, followed by a research centre). Further proof that the castes are more of a way of life rather than a predetermined path that every Skrell must follow without any deviation.
- Qerr-Katish (High Caste): Considered as the leaders of Skrellkind, the Qerr-Katish are the face and soul of Skrellian society. Managers, diplomats, lawyers, they are notably the only caste allowed to fulfil the role of Qerr-Skria, and the only one forbidden from being appointed to the Xaq Moglar. As the representatives of the Skrell, the Qerr-Katish are highly social beings, sophisticated, cultured and very organised. As defenders of their society’s values, they tend to be rather conservative, although progressive ideas regularly grow within the caste, as a stagnant society is a dying society. Considering their role, they are generally the richest people of a City-State, although their money is generally invested in various endeavours both in and out of Skrellian society. Qerr-Katish families tend to be rather small, being generally limited to one, sometimes two bondings. They often dress in clothing made from softer, shinier materials that are long and flowing and have often been compared to the clothing of ancient Chinese nobles by human scholars. Their skin is generally bright green.
- Malish-Katish (Caste of the Mind): If the Qerr-Katish are the face of Skrellkind, the Malish-Katish are its brain. Scientists of all sorts, researchers, scholars, they are the ones who allow Skrellian society to grow, be it technologically or ideologically. Highly inquisitive, they are among the more progressive and individualistic Skrell. They are, however, not very social, and their emphasis on methodical, rational thinking make them less capable of being under pressure and handling their feelings in public. Although they are less wealthy than the Qerr-Katish, their usefulness allows them much comfort and status in Skrellian society. Their families are generally made up of two or three bondings, frequently from different partners. Skrell of this caste often wear clothing made from the same materials as the Qerr-katish yet simplified, white shirts and black pants with possible jewellery for decoration. Their skin is generally pale green, sky blue or pale yellow.
- Kanin-Katish (Caste of the Builder): The main workforce of the Skrell. While their population growth has decreased over the millennia of technological progress they are still one of the most populous castes. With activities ranging from goods production and services to engineering and construction they occupy the largest and most diversified sector of Skrellian activity. The Kanin-Katish are a very tightly knit community, both within their families and with their coworkers. They possess a strong mental and physical resilience. Very traditional, they hold rather conservative views on the world, and their focus on the whole rather than self dampens much of their individualism. Their families are frequently large, three or four bondings, generally with a couple of partners, which does not leave them much in terms of money. The Kanin-Katish are among the less wealthy people of skrellkind, but they do not seem to mind, as their work is the life and blood of Skrellian civilisation. Their clothing is made to last, the personality of the Skrell often being shown through arm bands or headtail decorations of any kind. Their skin is generally red, orange, pale yellow, dark orange or black.
- Talum-Katish (Caste of the Artist): Considering the Skrells' emphasis on functionality and practicality, one would be mistaken to think they do not consider arts much. This very important sector of Skrellian society is handled by the Talum-Katish, artists, aesthetes, entertainers, chefs, actors, writers, singers. They somewhat compete with the Qerr-Katish’s role as representatives of skrellkind, although in a different way. As such, they are often mistaken for Qerr-Katish themselves, which might explain why this caste is generally seen as rarer and less celebrated than the others, while they are in fact frequently on the public scene. The Talum-Katish are the most individualistic members of skrellkind, although once again, they share the Qerr-Katish’s taste for a busy social life. Highly cultured, they are the free-thinkers of Skrellian society, often at odds with more traditionalist and conservative castes. A heterogeneous lot, it is hard to estimate their global financial capacities, they however tend to reproduce a lot, multiplying their encounters with various partners, which might put a strain on their savings. Their clothing is often an odd mix of Qerr-Katish and Kanin-Katish, as they often wear clothing that is colourful , adorned with embroidery and their headtails sparkling with various brilliant metals. Their skin is generally purple, blue, pink, orange, red or white.
- Raskinta-Katish (Caste of Warriors): Rarely seen outside the Skrellian society, the Raskinta-Katish are however recognised and respected by their entire species, for they are the ones who ensure the safety and stability of Skrellian civilisation, both against internal and external threats. The military caste of the Skrell, most end up working for the various city-states, either in the police or as a career soldier, although some of them end up working for private security or as entertainment fighters. They are very conservative, almost reactionary, and deeply committed to their community, caring very little for self-development and personal satisfaction. Their martial training leaves very little time for most intellectual pursuits, although they are trained to be expert tacticians and are only beaten by the Qerr-Katish in terms of organisational skills. While they are wealthier than the Kanin-Katish overall, they are still among the poorer castes of skrellkind and their large families of three or four bondings put a heavy strain on their earnings, only compensated by their strong social cohesion. These are often the hardest to spot among a crowd because they intentionally wear clothing other castes are known for while not working, however they tend to stick to clothing that is easy to move in and are often dark blue. Their skin is generally green, blue, black, brown or yellow.