A Twi'lek native of Ryloth taken from her home by slavers, Oona had the good fortune to be freed by Jedi master Trisko Drall during his anti-slavery campaign in the Outer Rim. When the Master sensed her force potential, he asked her if she wanted to return to her home or come with him to Coruscant. Oona chose the latter; but it is a choice that has haunted her ever since – visions and dreams of other Twi'lek suffering the ignominies of slavery continues to haunt her even today, and she has been known to react very harshly indeed against slaves – even suspected slavers. Master Oona Dio has spent much of her life away from Coruscant, ceaselessly bringing justice to the Outer Rim and beyond – she does not feel that the Force is limited by political borders, and has in the past taken actions in systems not affiliated with the Republic.

Oona is very tall for a Twi'lek. Her lean frame is covered by supple muscle, which is further enhanced by the tight-fitting black body-suit she wears. She is a true Jedi Guardian - a master of the lightsaber and a staunch defender of the Republic and the values of democracy and freedom.