During and for a time after the Sundering, magic ran wild across the world. These fluctuations were responsible, in part, for the current speciation we see today.
On the largest island in a chain of free floating islands arose a vibrant and proud species of snake creatures. They were small and insignificant before, but now they stand taller than a man. With a scaly, reptilian head and torso resembling that of man and the long, powerful body of a snake. Feathers grow from the nape of the neck and down and around to the collarbone in a shape the Es'ka refer to as 'the divine crown.' Feathers grow from the head in long sweeping waves and are often cut, styled, and adorned. In some, feathers can appear in other places, such as the tops of the hands, down the spine of the back, or on elbows or shoulders.
The Es'ka all spend the first 3 years of life as a very snake-looking creature. They hatch under the care of a special caste of males (more on that later) and slowly exhibit their final appearance over several moltings over a total period of 10 years. Upon an Es'ka's 10th year (approximately), they enter a special molting period (1 week) where they transition into a female. Any number of days, weeks, or months may pass before a female grows and self-fertilizes a clutch of eggs. It depends on various factors and years can pass before the process occurs. But when it does, things get interesting. After laying a clutch of eggs, a female will enter a special molting period and transition into a male. If it happens after the first clutch, that male enters something like a warrior caste; this is most common. If it happens after the second clutch, they are military leaders, officers, and strategists. If it happens after the third, they enter the special caretaker caste that raises the young. It's rare for an Es'ka to have a fourth or even a fifth clutch of eggs, but when it does happen those Es'ka are especially revered. Once every 50 to 75 years (3 to 4 generations), the Es'ka enter a special mating period where the males grow genitalia and attempt to mate with as many females as possible.
Historically this has been a bloody orgy, with the society risking constant collapse. As a result of their mating habits and intense isolation from outside forces, a complex social society has been developed and the Es'ka are internally stable during the periods leading up to their technological upheavel (~300 years).
----------------------------------------
{from the journal of the Novir, York the Better Mannered}
"I never expected to be pulled from the airship by snake-men wearing feathers and gold, and hissing at me like they wanted to throw me into a pot. I struggled at first, but they were far too strong for me to overcome. I was terrified and I am not embarrassed to say that I begged for my life. They carried me and I knew who not else along to a grand stone archway carved, I swear to our Most Wise Father, into the side of a burnt out volcano; except the land had collapsed away and left standing half a volcano. And we entered, not from the side of the volcano like a sensible person, but by going around and entering from where the other half had broken away. The blood was pumping in my eyes when I looked down and saw nothing but mist and darkness below as the snake-man carrying me slithered over and around a massive stone outcropping.
Despite my fear, they were never so much as unkind to me. Unceremonious, but not unkind. When we reached our destination they threw me and a few others to the floor. The shipwright come blacksmith, the captain, and a fellow traveler. A few of the snakes examined us and tended to our wounds. They gave us water and a spicy rabbit stew. After we saw to our needs, we were guided to another chamber and made to take what I supposed was a reverent pose. I would learn later that the feathered snake-man before us was Es'sat the Curious, an Es'ka who bore 4 clutches of eggs. He was also responsible for expanding the territory of the Es'ka by constructing rope bridges from one island to another. He was highly intelligent, highly skilled, and highly eccentric, even among the Es'ka.
He examined each of us closely. When he got to me he coiled around me, as he had done the others, and touched me all over. Often he picked me up and moved me around. Examining my face and looking into my mouth. He looked closely at my hands and at my feet. I was like but unlike the others and I must have been fascinating to him. He looked closely at my shell then, and opened one of my drawers. He stopped his erratic hissing and slowly set me down as he pulled the drawer completely free. Inside it I knew were a few small rolls of parchment. Scribbles and notes. I knew he couldn't read the writing on it, and it was insignificant in any case, but it sent a chill through my hands. His reaction - it Knew. It smiled like when a person smiles and it was terrible. When he looked at me I could see that he knew that I knew.
The terrible weight of Fate comes but once a lifetime and my Lord has asked me to witness the birth of a new civilization. I thought then that this snake-man would bite and rend every bit of useful information out of us and all the unimportant bits too. I didn't realize how right I was. Es'sat the Curious, it turns out, was on the committee of language and helped develop the Es'ka's written script. He had argued for the importance of mathematics and engineering. We would provide a valuable source of information. On the state of the world, language, history, the customs of others, technology, and about the theory of magic."
----------------------------------------
Over the next few decades after York's arrival, the Es'ka saw a technological upheaval. The Es'ka had learned much from the crew, all hands told. They mined the earth for its iron and forged weapons of war. They took their chain of islands and connected them with giant metal chains. At first they experimented with airships and later built efficient two-man raiding vessels and large cargo ships. Then the engines were finished. Large, elemental-powered engine rigs carved into stone, at least one to each island. After a transitionary period and some testing, the Es'ka began to migrate their island off the layline it travelled upon and out into the world at large. There they pillaged and enslaved. Iron became more valuable than gold to the Es'ka and they adopted a currency system based around little shards of stamped iron.
The crew from the crashed airship were the first slaves on the floating archipelago. They were clothed and fed, and given jobs and some degree of respect. The Es'ka seemed to realize that their ways and customs were far too different from the strange otherkin. They recognized that they got the most out of the slaves when they were treated well and their skills utilized. Eventually the slave caste was mostly controlled through economic means instead of a vague threat of harm.