Originally after the storms they forced themselves into a state of isolationism due to the rising conflicts in the other galaxies. They even abadoned trade for a moment so they wouldn't have anything to do with anyone outside the Tholian Assembly, however this did not last long due to the fact Nod terrorists began attacking various worlds belonging to the Tholians, as well as abducting civilians for experimentation due to their crystalline biology. The Tholian Assembly went into panic, wanting to make peace with Nod but all attempts had failed, due to this fact their allies the Romulans sent in Tal Shiar Agents to kill and destroy the Nod encampments. After a group of sporadic meetings in the assembly, the Tholians reluctantly joined the Coalition.
A living Tholian was approximately the same height as a Human. It was principally a reddish color, in varying shades, and there was the suggestion of fluid or field motion within the body. Tholians had a hard carapace that was chiefly mineral. There were six thin legs that made it possible for the being to move in any direction quickly; the legs were articulated with joints roughly corresponding to the knee and ankle of humanoid species. Each leg ended in a multi-toed foot. The legs were attached at the base of the torso and were radially symmetric. There were two arms; each had joints analogous to the humanoid elbow and wrist, and each arm ended in a multi-fingered hand. There was no neck; the term "head" did not apply. Tholians had two glowing spots near the top of their torso. They turned these to face individuals with whom they interacted, which suggested they had some sort of information-gathering organ. Tholians did have two sexes, but each individual had both sets of sexual organs
Tholians existed at high temperatures – in excess of 450 Kelvin (177 °C, 350 °F). They could tolerate lower temperatures for a brief period of time; if they were exposed to too low temperatures, their carapace would crack. This was painful or distressing; a Tholian subjected to such a temperature regime could be coerced to cooperate. In temperatures even lower, a Tholian would freeze solid and shatter. Tholians had something analogous to biochemical processes. Tholians were naturally able to emit various forms of radiation, which they could modulate. They could communicate over short distances in this fashion, this has made them perfect spies for many sides.