The Physarai are shape-shifters, though they have limited control of fine detail in their forms. At rest, they are shapeless masses of about two and a half cubic feet of blue-green translucent gel. They do not have control over the colour of their forms without genetic engineering, but in deference to the abundance of bipeds that now occupy Thet, they most often choose to take on a bipedal form, typically with sufficient quality and skill for most other creatures they encounter to assume this is their natural shape.
The Physarai are an unusual case in communication and memory. As they are less developed than other sentient species in many ways, knowledge must be related to historical and episodic memory in order to be recallable. As a result, they pass on their information in the format of stories. This typically takes about ten tgc to do correctly, though end-to-end the stories would only take about half a year to communicate. The high number of repetitions helps to ensure effective communication.
The Physarai are one of the few cases in the universe where the evolution of sentience on a planet was not hindered by the presence and success of another intelligent species. Evolved from a gelatinous mould used by the Tletkettoyi as a food source, the Physarai developed towards self-awareness in the short period of time after the Tletkettoyic extinction event before the Lilitai arrived.
At first, the Physarai were merely shapeless blobs that moved over the ground in search of nutrition. They huddled around the radioactive remains of certain Tletkettoyic power generation systems for warmth, unwittingly exposing themselves to the powerful mutagenic effects of the strong beta emitters inside, and would occasionally go out to locate food, which mainly consisted of fast-growing autotrophs (blackish mosses) that grew near the edges of bodies of water. The Physarai that were able to remember the river's location and their warm home were better able to succeed, and this eventually drove them to obtain what we would call animal-like intelligence.
The primary force that drove their evolution after this development was the need to compete with one another, not evolutionary pressure from some outside force. This normally does not occur in evolution, as superior traits can be expected to simply beat out others, but the rapid rate of mutation and asexual reproduction meant that as many as a dozen different strains could co-evolve without actually succeeding in displacing each other completely.
Physarai evolved stronger and stronger senses of self-awareness. When the Lilitai settled on Thessia Major and began to set up camps, a Physaru or two would occasionally slip into their supplies and attempt to steal from it; the Lilitai found it quite curious how quickly the gels began to learn how to avoid detection, and eventually caught one or two for further study. It was not, however, until the Lyrisclensiae reached Thet that the Physarai were trained to assume a more humanoid shape and to communicate.