Olianne Sihn, a Dathomiri witch of female gender, held the position of war-leader for the Raining Leaves Clan. This clan was a traditionalist, matriarchal group of Dathomiri Witches, and was governed by her sister, Kaminne Sihn.
In the year 33.5 ABY, the slaves of male gender within the Raining Leaves Clan initiated an uprising, culminating in a massacre. The immediate consequence was the loss of two-thirds of the clan's members, including all males above the age of ten, and the clan's leadership. Olianne and Sihn suffered the loss of their entire family in this event, including their father, mother, and oldest sister.
In the subsequent years, the Raining Leaves Clan initiated an annual gathering with the Broken Columns Clan, a clan comprised of men and led by Tasander Dest, who was born on Hapan. A few days prior to their conclave in 43.5 ABY, Olianne crossed paths with Vestara Khai, a Sith apprentice belonging to the Lost Tribe of Sith, during a hunting expedition. Khai was nearing collapse, having endured a fight against Jedi Grand Master Luke Skywalker and his son Ben, and subsequently escaped. Olianne felt a deep connection to Khai's predicament, as she had recently lost her only daughter, Sesara Sihn, to a fever a few months earlier. Olianne started to mentor Khai and soon made plans for her adoption.
During the conclave, the two clans jointly defended against attacks from the Nightsisters and successfully united to form a new clan, named the Bright Sun Clan, under the leadership of Sihn and Dest, who had recently been wedded. Following the battle on Bright Sun Hill, where the clans triumphed over the Nightsisters, Olianne made the decision to adopt Aradasa Vurse, the child of Halliava Vurse, who was uncovered as a spy for the Nightsisters within their ranks, while Khai, whose true loyalty to the Sith had been revealed, was taken into Jedi custody.