Manaan was an aquatic planet in the Pyrshak system. It was home to the Selkath, an amphibious species. The planet was completely covered in water and was the only known source of the medicinal substance kolto in the galaxy.
Controlled by the Rakata during pre-Republic history, it became independent following the collapse of their Infinite Empire. In the years leading up to and during the Jedi Civil War, kolto was so important to the galaxy that the Selkath were able to use their monopoly to enforce their policy of neutrality and autonomy.
The only above-surface settlement on Manaan was the floating Ahto City. During the Jedi Civil War, both the Sith Empire and the Galactic Republic attempted to get an upper hand in the war by creating secret deals that would give them more kolto. Ultimately, however, the Selkath banned the Sith from Manaan for trying to overthrow the government.
When kolto was replaced in favor of bacta, the Republic abandoned Manaan, and the Selkath left Ahto City for their ancient cities in the depths of the planet’s oceans. Manaan did not have further contact with the galaxy until the Selkath were enslaved by the Galactic Empire sometime during the Galactic Civil War.
Under the manipulation of Darth Vader, the Order of Shasa later overthrew their Imperial masters, only to become servants to Darth Vader and Emperor Palpatine.
After the Galactic Civil War, Manaan joined the New Republic and has since re-opened Ahto City to surface dwellers as a resort for tourism.