These creatures are a species known as the Daraz, and they are monotremes, a.k.a. egg-laying mammals. The Daraz come in four basic body types: Kiralyno (a.k.a. The Kira, the primary egg-layer); Hazastars (consorts to The Kira who are involved in reproduction); Munkas (non-reproducing laborers); and Harcos (non-reproducing warrior/hunters).
Of these, the only ones humans are ever likely to see are the Harcos, as the rest typically stay underground for most of their lives.
Your body type, and therefore your caste, is preselected at egg-laying based on what the clan needs most. Every egg has the potential to be any body type. Which one it grows into is determined mostly by what the embryo is fed while it is developing in the cell. Some will get a diet rich in thus and such hormone, and become breeding adults. Others will get a different hormone, and become non-breeding workers.
Daraz society is collectivist – you have a job to do for the good of the clan as a whole, and there’s not much room to decide you want to do something else. After all, if you’re a non-breeding worker caste, you do not have a reproductive system (beyond some vestigial internal organs). You can’t decide you want to be a breeding adult instead. If you are a Harcos your body is literally a weapon, and you will be expected to train in how to use it so you don’t hurt those around you just by existing.
Ah, but biology is complex and prone to unpredictable variation, and as such this predetermination process doesn’t work smoothly 100% of the time. Up until about 6 weeks of gestation you can switch production over to a different body type without noticeable consequence. After a somewhat vague cutoff point, though, you wind up with someone who is a little bit this and a little bit that. These Daraz are known as “Keverek,” a.k.a. “mixed.” In these cases, you’re assigned to the caste you seem most similar to, and everyone just sort of hopes it works out.
Hali is one of these Keverek. Xe started out on the path to being a Hazastar, but a sudden need for more Harcos had xer production shifted fairly late in the game. Since Hazastars are significantly smaller and less muscular than warrior/hunters, Hali is shorter and thinner than xer compatriots. (Xe is also much younger than the other two in the illustration, who are adults tasked with training the up-and-comers.) Given that xe has all the Harcos weaponry and no evidence of a functional reproductive system, xe was assigned to the Harcos caste, and off to training xe goes.