Silentium

The Silentium are an extra-galactic droid society.

Details
A species of star-shaped organics created the droids to resemble their form, in much the same way that sapient humanoids created bipedal droids. After the organics were wiped out by a radiation storm from a nearby supernova, their droid creations lived on.

These droids continued to reproduce and improve themselves, and developed a culture based on the prime numbers of five, seven, and eleven. Many of them took on the form of geometric shapes, with the circle being the "holiest" of shapes. Thousands of the wisest members of the droid race created powerful fifty-kilometer spheroid bodies. Two influential members of this giant variety included The One and The Other, and the others were collectively called The Rest.

This new culture of order and symmetry soon brought them into conflict with the chaotic, self-constructing droids known as the Abominor. The two droid species fought a galactic war, ignoring their galaxy's native organic species, until the organics fought back and forced both droid powers to flee their galaxy.

The Silentium soon found another galaxy to call home, and settled in a place that Humans would come to call the Unknown Regions. Their reclusive and conservative lifestyle eventually caused them to grow bored, and they created young droids in the image of their organic predecessors to explore the galaxy.

Some of these infant droids were deposited in the oceans of Mon Calamari, as the mechanical creatures known as nano-stars resembled the description of the star-shaped race and were deposited by a giant metallic sphere. The scout known as Vuffi Raa went on to have a wide variety of adventures with numerous masters, including Lando Calrissian.

The Silentium eventually sought to reclaim their "child", and they revealed themselves to the greater galaxy in the Battle of ThonBoka. After displaying their power by destroying the Imperial cruiser Recalcitrant, they took Vuffi Raa back with them.

The Silentium allowed Vuffi Raa to return to visit Calrissian on several occasions, and the massive spheres continued to be sighted around the galaxy, including a sighting by a hundred thousand beings during the Priole Danna Festival on Lamuir IV. They showed no interest in becoming involved in the affairs of the galaxy, though the location of their new home system is believed to be somewhere in the outer rim.

Behind the scenes
The sightings of Silentium across the galaxy as stated in The Essential Chronology were intended by author Daniel Wallace to reference contemporary UFO sightings.

The war between the Silentium and the Abominor is strongly implied to be the root cause of the technophobia of the Yuuzhan Vong, according to Dan Wallace's endnotes for The New Essential Guide to Droids. This was later confirmed in the second part of the blog series The Droids Re-Animated.