Yeerks reproduced in threes, decaying as their offspring were created. Essam 293 was the child of three unassuming low-ranks who had been born well before the war and were out of place during it—to say nothing of time. His siblings, by and large, were complacent with life, few aspiring to higher ranks.
Once he realized this, even if he couldn't articulate it, he spent as little time in the pool as possible. He would access every data file he could find, regardless of what it was portraying. His poolmates didn't seem as interested in it as he was, but he didn't mind. It meant more time with his palps plugged in.
He thought that his first time inhabiting a Gedd wouldn't be very different from the computer, but it made the simulation feel like the Yeerk pool. He was in utter control, able to walk about and change his points of view. More than that, he had access to another being's thoughts! Primitive ones, but nevertheless the most stimulating moment of his life.
But after that, he had to return to the vicarious digital world. He spent far more time there than his siblings; whenever they had a question about the computers, they came to him for advice. Once he got his first long-term host, a Taxxon, he naturally chose to train as a technician. As soon as he began study, he realized that all of his "expertise" was trivial. Still, he pressed on, quickly attaining certification.
Nearly as soon as he made Under-Visser, he was transferred to out-of-the-way Anmar base. Two of his sisters were also transferred there, but they were as shortsighted as they'd been in the pool, settling in without further aspirations. There was little for him to discuss with them; "It's really a shame our twin brothers were Draconed for treason by incompetence" didn't make good pool conversation.
The base was worthless, and all the technical ability in the world wouldn't get him out. He doggedly retrained as a pilot, flying transport ships through Z-Space. Menial work, but he did it well. Soon enough, he was occupying a Hork-Bajir, and had been promoted to Sub-Visser Three-hundred-ninety-one.
It was on (or, arguably, slightly above) the moon of Cerba that the incident occurred. Essam had flown a ship to the quiet moon, where he outranked all but two of the Yeerks assigned, some time previously. But a Zero-space rift between Cerba and the Yeerk-controlled planets was widening, and he was happy to stay temporarily. If nothing else, it was better than Anmar. With his technical services in little need, Essam was assigned to atmosphere patrol duty.
The Desbadeen vessel taking off was inconsequential enough. It had stopped by from beyond the Empire to trade for food, with several of its limner crew entering the pool to get said food. Like the Skrit Na, the Desbadeen were unfit to infest because of their drastic metamorphoses; while the limner were sleek quadrupeds, the carapa were barely mobile. The two forms were segregated as much as possible, which led to their inefficient ship designs. While they made nice mercenaries, they did not need to be conquered, and were officially considered neutral.
The Desbadeen promptly paid for their sustenance. The captain—a limner, of course—notified Essam that several Hork-Bajir Controllers, who had previously volunteered to help the Desbadeen carry their food out to the ship, had chosen to travel aboard it and would be disembarking elsewhere in the system. He had no reason to interfere with the neutrals' business, and let them depart.
It was only later that day that several well-fed Yeerks realized that their hosts were missing. The Desbadeen were long gone, and Essam took the fall. Demoted to Under-Visser, he was sent to the dead end of Olgin base.
He was treated like a new recruit despite his experience, forced to put up with Sub-Visser Four-hundred-nine's indoctrination. She seemed to delight in nothing except flaunting her power, never mind that some of her students had formerly outranked her. While most of his peers were hapless low-ranks, there were several others like him, who had gone from being moderately-powerful Yeerks to hopeless low-ranks. He could have easily followed them, tolerating the stifling bureaucracy, apathetic to the future of the Empire. His life would have been quieter. Safer.
He didn't.
He made friends, or pretended to, as many as he could. There were few on Olgin base who had the power to send him elsewhere, but their allies could. And Sub-Visser Four-hundred-nine? Perhaps her frustration was not with him and the other recruits, but with the system that was wasting her ability.
He saw her access the computer files, analyzing the path of a Skrit Na vessel. Casually, he volunteered any help he could offer. Some time later, she asked him if he could write some programs for her, finding optimal conditions for life in systems near the trajectory. Always politely, never asking what she was doing, he helped her search.
Edriss came to him after a meeting with an indolent double-digit Sub-Visser more dejected than he'd ever seen her. He asked no questions, simply promised to help in any way he could. By the time night fell upon Olgin, they were deep in Z-space.
His navigation was flawless, but no being could outfly the burgeoning dimensions of Z-space. By the time they emerged into the first system they wanted to visit, their host bodies were a feeding cycle away from dehydration. It had been a long journey, with more than enough time to research, as he had impulsively done, their would-be impediment to progress...and their catalyst to begin the voyage.
It made perfect sense, in retrospect. His sisters were nothing if not chatty. They knew plenty of Yeerks, and one of them had known enough Yeerks in power to rise to the rank of Sub-Visser Seventeen.
Yet while Essam 293's formative generations had been trying, nothing in them had broken his spirit as utterly as he felt on the Anati planet.