The crystalline Chenjesu.
The Chenjesu are a race of silicon-based, crystalline beings native to the Sapphire World of Procyon II. They are photo/chemovores, and have no natural predators, nor need for prey. They are naturally non-hostile.
They also have natural receptors in the HyperWave band, which gave them the first inkling of the Ur-Quan invasion. They formed a military alliance with the Mmrnmhrm to form the basis of the Alliance of Free Stars.
The Chenjesu, while silicon-based, are not at all like the Taalo — Chenjesu are crystalline rather than rocklike. Their starship, the Broodhome, possessed more raw power (and raw material) than any other Alliance ship, even if, in general, it was not the most effective in combat.
Images of the Chenjesu captains imply that they have limited control over electrical discharges, which they use to control their equipment.
After the Sa-Matra was deployed against them by the Ur-Quan, they and the Mmrnmhrm requested to be shielded together on the Chenjesu homeworld. The Ur-Quan permitted this, and once on the planet, the two races began a synthetic hybridization of their species, which they called "The Process". However, the Process was interrupted prematurely by The Captain, resulting in the hybrid race, the Chmmr.
The reasons for this are fairly clear for the Mmrnmhrm, as that race had lost the ability to reproduce on its own. The motivations of the Chenjesu are still unclear. The Role Playing Resource Guide indicates that the Chenjesu probably decided to do this because they felt their culture had become so advanced that it had stagnated entirely, and that the modification of their species into a transChenjesu synthesis would reinvigorate their society. Their motivation probably also had something to do with defeating the Ur-Quan.
The Chenjesu were respected and admired by the other races in the Alliance, and many considered them its leaders, although they refused to take that title officially.