Death is just the beginning...
Darth Banshee was a Trandoshan female Sith Apprentice in 129 ABY. She was one of ten apprentices trained by Darth Echo for his new Sith Order. Her favored Force Power was Force Scream, yet like her other apprentices, she was trained into immortality by Echo when she learned Force Phoenix.
Vosha J'tarr was born in 227 BBY to a young Tranoshan woman named Kortha J'tarr. Her father was Nalrik J'tarr, who was a then-redeemed Sith Lord (He left the Sith Order when he met and married Kortha). In the year 207 BBY, Kortha was killed when a group of Jedi attacked her home, believing the Ex-Sith lord Nalrik to be alone at his family estate. Without searching the location, four Jedi Knights who were led by Master Jaxor Dezali used the Force to crush the area around the building, fatally wounding Kortha. The Jedi left the area without searching for her body.
Nalrik and Vosha returned to their home to find it destroyed. Nalrik ran into the remains of the building to help his wife but she was too close to death. The moment she died Nalrik felt a familiar sound. the echo in the Force that called to him before. He walked out and looked at his daughter. He told her of his past, he told her everything.
Nalrik J'tarr died again that night and Darth Echo was back. Wracked by vengeance and thirsting for the blood of Jedi, Vosha joined her father in his bloody quest of hatred and suffering. She named herself Darth Banshee, and trained herself into adapting Force Scream, a power magnified by Darth Echo's teachings. Darth Echo himself taught his daughter his secret to immortality, and told her that she was the first apprentice in his new Order.