"The militant religious order of fanatical man-size insectoid full-body cyborgs" is the most compact description of the Children of the Source. Of course, it is not the same answer as the typical member of the order would give you. And the one you would receive today isn't what you would hear from them some thousand years ago. Therefore sit comfortably, bring a drink, and dive with us into the deep and murky waters of history, evolution, and the present of the Children of the Source. The story of the order reaches into the ancient biological time of the founder race. Many researchers believe that the founders lived in a typical eusocial society with a caste system and roles given by specialization of the body type on the concrete hierarchical level. But researchers tend to overcomplicate things, so instead, imagine a beehive with the queen, workers, warriors, and so on, and let them evolve into a space-faring civilization.
Somewhere along the way, the species must have lost the ability to reproduce. Maybe the queens died or were overthrown by a lesser cast or another species. Your guess is as good as mine. But one thing is certain: facing extinction, the members of the species began to prolong their lifespan at the cost of their biological bodies, and in the end, only the full-body cyborgs remained. The effort exhausted their home planet which was the cause and the very beginning of the interstellar crusades.
Yes, there is the official liturgy that claims the reason for the crusades was seeking the lost goddess-queen the Allmother and she sleeps somewhere in the Siren System. Speaking of Allmother, the unforgiving, bloodthirsty, malevolent creature demanding absolute subservience, usually depicted as 20ft tall, steel statue with sharp spiky limbs and the kind smile of an Asian giant hornet, one can only hope they will never find her. But back to the crusades.

Shaped by evolution?

Regarding the look and limb count of the Children of the Source, the crusades must have targeted more insect parts of the galaxy or by that time the order considered assimilating the non-insectoid species inappropriate. In short, they followed the rule If you have less than 6 limbs you probably have no soul and cannot play with us. That mirrors even the constitution and look of today's Children of the Source warriors. Shiny metal armor substitutes the chitin exoskeleton, tiny multi-lens cameras are in the same places as the compound eyes would be, and even the ceramic mandibles are present despite the cyborgs rarely needing to cut the food to bites.
The story continued like that for quite some time, till the Children, now possessing a gargantuan fleet and endless numbers of warriors, reached the Siren System. There, an irresistible force met an immovable object. Ancient Primals, with their superb crystal-based technology and deep understanding of psionic powers, were the bite the Children could not swallow. Even though the warriors of the order were far from the mass swarm attacks, so usual for insectoid species, and relied heavily on smart tactics, technology, and the quality and strength of each warrior, Primals were more than capable of resisting. The momentum of the whole crusade discharged on the single solar system. The price both sides paid was enormous, the entire race of Primals perished, their cities in ruin, planets emptied, and ecosystems broken, but Children of the Source were stopped, their fleet turned into derelicts orbiting the planets and the order was reduced to a fraction of its former power. Yet not all the Children were destroyed.

The Children today

The last millennium went in a spirit of restoration. Unable to assimilate more members, the Children's only means of replenishing numbers was to roam the old battlefield, and starship derelicts while looking for anyone they could repair and re-awake. Despite the circumstances, their numbers steadily grew and the wonder of the Temple City emerged from the desert as the last bastion of hope for the order. The Children have even found new enemies. The Tumori tribes, a race of parasitic aliens, arose from the toxic jungles like a twisted joke in the high culture of Primals expense. The last topic we will cover in this article is the present situation of the Children of the Source. It is difficult. After a series of defeats and without the means of reproduction the order stands on the verge of extinction. Paradoxically though, the most severe defenders of old ways perished in the last years, and the arrival of the two organic species to the Siren system started the process of change. Children opened their religion to the newcomers and swiftly persuaded the UNSS and the Fossorians to form an alliance. They have even opened some parts of the Temple City to outsiders.
A new era has begun. The Children of the Source are trying to assume the role of defenders of peace and while facing extinction show a kinder face to the world. And we all truly hope that they will stay on their new path and will not stray to the old one. Now, before you enter the Temple City, forget all you have just read! The Zieregals, the order inquisitors, will ask you many uncomfortable questions and they dislike biological creatures knowing too much from the secret history of the order.