Dynassia is a class M world located near Federation space. Prior to the bombardment of the Iconian homeworld approximately 200,000 years ago, there was an Iconian outpost present on the planet. When the Iconian homeworld was attacked, along with Ikkabar and DiWahn, Dynassia was one of the three worlds that the surviving Iconians escaped to via an Iconian Gateway. Unlike the other two worlds, there was already a native population living on the planet.
The Iconian survivors, who became known as the Dynassians, were able to successfully adapt to this new environment, although there was a great deal of tension between the Iconian descendants and the native population. A group of leading academics ruled the planet in an assembly called the Faculty. The head of state of Dynassia was the Warden.
In the mid 24th century, Dynassia had applied for admission to the United Federation of Planets, which heightened tensions on the planet. After a group of Dynassians attempted to retrieve the Devil's Heart by hijacking a Federation starship, the Federation Council decided that Dynassia would be ineligible to apply for Federation membership for at least 100 years. (TNG novel: The Devil's Heart)
Like the DiWahn and the Ikkabar, the Iconian descendants of Dynassia developed their own distinct language, based on the original Iconian mother tongue. In 2365, Lieutenant Commander Data was able to use the Dynassian language, plus the languages developed on Ikkabar and DiWahn to help reconstruct the Iconian language. (TNG episode: "Contagion")