The pale and ghostly Umbarans are an extremely high tech species who have decided that the Separatists are a more worthy group to follow than the Republic. At one time represented in the Galactic Republic by the devious Mee Deechi, Umbara seceded from the Republic and joined the Separatist cause. Their advanced weaponry proved a great challenge to the clone troopers tasked with conquering Umbara.
Umbara, known as the "Shadow World" due to the rays of its sun never completely reaching its surface, is perpetually dark. The native wildlife have adapted to survive in such gloom, making the planet perpetually dangerous. Umbara was once part of the Galactic Republic, represented in the Senate by Senator Mee Deechi. Later in the Clone Wars, the planet's loyalty wavered and the natives of Umbara allied themselves with the Separatists, bringing their extremely advanced technology to the Separatist Alliance.
At the time of their introduction, the Republic clone troopers represented the future of galactic warfare. Far superior to battle droids, the clone troopers formed the backbone of the Republic's new military that waged war against the forces of the Confederacy of Independent Systems. So symbolic were they of the times, the galaxy-wide conflict that saw their debut took its name from their ranks: the Clone Wars.
In the final days of the Republic, the galactic government had grown so huge and corrupt that any attempt at change required radical thinking and extreme actions. Outlying systems that saw no benefit from being part of the Republic despite paying heavy taxes, began to rebel. This undercurrent of disgust towards Coruscant was seized by a charismatic leader, Count Dooku. The former Jedi rallied together these worlds in a Separatist movement that saw the departure of thousands of systems from the Republic. When Dooku's alliance was secretly backed by corporate titans that offered their unlimited droid armies to the cause, the Separatists emerged as a major threat to the Republic, and the galaxy tipped towards full scale war.