Kruskalia

The Kruskalia were sensitive single-cell organisms. Despite the fact that they were a virus, they were sentient. The species as a whole used the dark-side. They could infect most species, but normally they infected humans, taking control of the body. They would use their human hosts to refer to themselves as "Kruskailia". It was their goal to conquer the largest area that they could, which became the galaxy once hyperspace was discovered.

Biology
Being single-cell organisms, the Kruskalians were powerless to do anything without a host. Once they found a host, they would completely take control of the body and the mind. They used their hosts to reproduce sexually, creating offspring of the hosts born with the Kruskalia virus. They were able to access the memory of their hosts, and use them to give the appearance that the host was uninfected, allowing them to maintain secrecy. However, many affiliates of the infected ones had been known to comment on a "change in personality", normally for the worse. It was also observed that many of the affliced had been seen together talking in a strange language. All Kruskalia had telepathic connections to something that they veiwed as God, a physical being, though its location was kept a secret. Many had theorized that if they could kill the creature, they could stop the parasite, though nobody had ever managed to find it. It was also noted that anyone who was born force sensitive was immune to the disease.

Culture
The Kruskalia had no formal culture, moral standards, or religion. Their "God" was supposed to be their leader; it issued telepathic orders to all Kruskalia cells simultaneously.

Plans
The Kruskalia's plan to conquer the galaxy was simple; to infect everyone vulnerable, and kill everyone who was immune. Some were trained to recognize the infected ones, though this knowledge was foolishly restricted to Jedi masters. Because of the secrecy, the parasite managed to infect entire planets. The Kruskalia killed any Jedi, Sith, or other force user whenever there was an opportunity. Most Kruskalians had access to lightsabers, and were indifferent to any pain their host suffered. This made an afflicted one an opponent with superhuman stamina, as they continued to fight through broken or severed limbs, severe blood loss, and even failure of the heart, though it would only last until the host died.

Defeat
By the time the Kruskalia had taken the Krashkiyov solar system, the republic sent a fleet on a top-secret mission to contain them by destroying any ship exiting the planet. Ultimately, the planets had to be destroyed.