The planet capital of the Thinking Machine empire, after the empire's re-birth after the defeat at the Battle of Corrin. The constructions on Synchrony were described as a series of free-moving and flowmetal machines that moved and assembled themselves into different shapes and buildings as commanded by the Evermind.
Re-birth of the Machine Empire
In the Prelude to Dune novels penned by Brian Herbert and Kevin J Anderson, one of the copies of Omnius on Giedi Prime launched thousands of deep space probes into the far reaches of the cosmos. Each of these probes contained the complete necessary thinking machine mechanisms to build a machine society. One of these such probes landed on the planet that was going to come to be known as Synchrony.
Over a hundred years later, near the end of the Battle of Corrin, the last copy of Omnius Prime electronically launched a signal copy of itself and all copies of the Thinking Machine empire, into deep space. This electronic signal degraded as it sped through deep space, and just before it faded into oblivion, latched onto the machine society that had landed on Synchrony.
Capital of the Machine Empire
Synchrony was far away from human-inhabited space, and there was no contact between human-kind and the machines for the first 10,000 years.
However, as humanity and the machine empire expanded towards each other over the next 5000 years, small amounts of contact begun.
One was Omnius and Erasmus on Synchrony included intercepting and altering the Enhanced Face Dancers. From Synchrony, they sent these Enhanced Face Dancers back into the Old Empire to infiltrate all levels of human government.
When the Honored Matres attacked a thinking machine world outpost during The Scattering, it was from Synchrony that the machines began the long war against humanity. This long war caused the Return of the Honored Matres, as they fled from the machines whom they dubbed the Enemy, as the Matres fled back into Known Space.
Also, from Synchrony, in their guise as Daniel/Omnius and Marty/Erasmus, an elderly man and woman; the duo attempted to capture the no-ship, the Ithaca, as they searched for the Kwisatz Haderach. The duo continued to cast their Tachyon net over and over for almost thirty years, attempting to bring the Ithaca into captivity.
Kralizec and the end of the Age on Synchrony
When the Machines finally captured the Ithaca, it was to Synchrony that they were brought.
These are the monumental events that occurred on the planet over a period of just one day during Kralizec --
Third was the death of all Enhanced Face Dancers as their leader Khrone, revealed their supposed takeover throughout the galaxies. Erasmus killed them all simultaneously throughout the universe using the Tachyon net, by activating his secret Face Dancer kill switch he had installed in them centuries earlier.
Lastly, Duncan Idaho, was revealed to be the Ultimate Kwisatz, as he accepted the codes and traits of Erasmus into his persona, just before the flow-metal robot decided to end his life.
The Future of Synchrony
While guided by Omnius, the machines and structures followed the Evermind's commands explicitly. After his banishment, and the rise of the Ultimate Kwisatz, the machines were given much more liberty to configure as they saw fit to express themselves.
Lastly, the sandworms released by Leto II and Sheeana, continued to multiply and became part of the eco-system of the planet.