The Amoniri were a civilization that belonged to the Breen Confederacy. Lacking blood, the Amoniri also required specialized modifications to the uniforms commonly attributed to the Breen to include refrigeration systems in order for members of the Amoniri to survive. If the Amoniri were exposed to natural air they would evaporate.
They, along with the Paclu, were one of the dominant members of the Breen military. (ST - Typhon Pact novel: Zero Sum Game) They were also dominant with civilian spaceflight within the Confederacy. (ST - Typhon Pact novel: Plagues of Night)
Amoniri had mostly liquid bodies that the refrigeration suits keep from evaporating, and their fluidic nature may allow them to better tolerate rough travels in space. They originated from a location that had a cold climate, which shows the necessity for their uniforms to be modified to have low temperature refrigeration. When an Amoniri dies an evaporation death, they feel a lot of pain as their mostly liquid bodies turn to vapor. They suffer a slow loss of physical function, and then ultimately descend into madness before finally dying and dissolve into mist. (ST - Typhon Pact novel: Plagues of Night)