Serenia is an Age of great natural beauty, with clear skies, and plentiful amounts of sparkling water running through a stone forest down to a crystal lake. It is one of the few known Ages written by Catherine, and is inhabited by a peaceful, spiritual people.
The Serenians are a peaceful, matriarchal society. The few who can be found on the temple island are "Protectors", an order of six women who perform rituals to preserve the memories of the deceased, and maintain the temple complex.
Serenia is composed of several islands in a large ocean. The link-in point is on the far end of an island used for ceremonial and spiritual purposes. A temple complex stands on the shore, and a series of paths wind through a forest of stone pillars, leading from the link-in point to the sea. Criss-crossing these paths are several irrigation streams, with adjustable dams installed at various points to control the flow of water into various areas of the temple complex. From certain vantage points, large boulders can be seen floating in the sky.
The temple complex features a large stone structure where members of the Protectors meditate and pray to commune with their ancestors. Two large flowers rest closer to the shore — these are the memory chambers, where the Protectors preserve the memories of deceased loved ones. One is in active use, but the other is older and decaying as the gases produced within it became toxic. Bathyspheres near each chamber allow the Protectors to retrieve the memory globes which hold a person's memories after they die. A waterfall between the two chambers feeds their root systems. A life stone, which is crucial to the chambers' ability to extract memories, sits on a pedestal in the pool below the waterfall.
Atrus and Catherine first visited Serenia with Sirrus and Achenar when the boys were around 10 years old. While they were there, they learned about many of the Serenians' traditions and customs. Roughly 10 years later, the boys returned to the Age in secret. They planned to convert the old memory chamber into a device that extracted memories from people while they were still alive, without killing their body. They intended to use this to extract their father's memories, allowing them to transfer themselves into his body. They would use this scheme to persuade the inhabitants of Atrus's Ages to do their bidding. Fortunately for Atrus, the two brothers were unable to work together long enough to see the plan to its fruition. Instead they unwittingly trapped themselves in Spire and Haven, leaving Atrus imprisoned in K'veer.
Twenty years later, Atrus and Catherine brought Yeesha to visit Serenia. She was taken with the idea of the memory chambers, and studied with Protector Anya to learn how to commune with the Serenians' ancestors in Dream. Within a few months, she had succeeded in her education and received a memory amulet from the Protectors. Less than a month later, Sirrus escaped from his prison on Spire and kidnapped Yeesha. He planned to use his memory chamber device to possess Yeesha's body, pretending to be her long enough to learn the Art from Atrus. He was ultimately stopped by Achenar and the Stranger, who entered Dream to remove Sirrus's consciousness from Yeesha's mind. In order to facilitate the Stranger's journey into Dream, Achenar had to insert the life stone directly into the old memory chamber's toxic heart, and he died from inhaling the fumes it emitted.