The D'ni are a race of humanoid aliens who lived in a subterranean cavern beneath the New Mexico desert. They are descended from the Ronay, and came to Earth around 9,700 years ago to escape the destruction of their original home world, Garternay.
The word "D'ni" (D'nE) is an abbreviated form of the phrase "new tree". It was a name chosen by the person who led their departure from Garternay, a great writer named Ri'neref. The name symbolized their separation from their brethren, who left Garternay to settle on the Age of Terahnee.
Unlike the majority of the Ronay, Ri'neref and his followers believed that the ability to travel to other Ages was a divine gift that should be exercised with respect, not abused and exploited for their own benefit. While this difference of opinion caused him to be expelled from the Guild of Writers, he and his faction were granted permission by the king to resettle on Earth, instead of joining the rest of the Ronay on Terahnee.
The average D'ni lifespan is 300 to 350 years. Visually, they are indistinguishable from humans, but often have a more slender build. Due to living underground for almost 9,500 years, they developed paler skin and eyesight that is more sensitive to bright light. Because of this sensitivity, many D'ni need to wear protective goggles when visiting other Ages.
It is currently unknown what the average age of sexual maturity is for a D'ni. It's possible that this occurred around the age of 25, given that the ceremony of readiness was performed at that age, and symbolized a child's transition into adulthood.
Women remained fertile until the age of 125, but could only conceive one day every two D'ni months—roughly 30 hours every 72 days. Gestation took a full year, and the DRC have uncovered no records of multiple births.
The D'ni are genetically similar enough to humans that they can produce viable offspring. The first known product of a human/D'ni pairing is Gehn. There are also indications that the D'ni could interbreed with other humanoid races as well.
Genocide and revival
In 9400 DE, on Leesahn 8, two criminals who had been exiled from D'ni society launched a devastating biochemical attack on their people. They killed over a million people, toppling the D'ni civilization and nearly caused their extinction. In the aftermath of the attack, only about two thousand survivors remained, scattered in various Ages. Many of these people were brought back together by Atrus approximately 70 years after the attack, in an attempt to rebuild their civilization in the cavern. These plans were ultimately abandoned, however, in favor of a new start on another Age, Releeshahn.