Members of the Tsol'aa race who decided to leave Sapience for parts unknown, the Tsol'dasi were once only spoken of as legend.
The existence of the Tsol'dasi was confirmed during the Death's Heart Saga, when a Tsol'dasi priestess, Pryla'ka, appeared to mortals and gave them aid in preventing the aims of the Quisalar.
It should be noted that the The Magisterion of the Underworld are Tsol'dasi. However, questioning them about their heritage would almost undoubtedly be a fatal mistake.