Vasti Idulia was a Jedi Knight that fell to the dark side of the Force, becoming a Dark Jedi. She is mostly known as the mother of Aalia Ra and, according to the Dark Jedi Archives, one of The Fallen Seven. The circumstances surrounding her life and importance as a Dark Jedi, as well as those of her death, remain to be a mystery. It appears as if her archival file is incomplete, as well as corrupted. The reason is unknown.
Not much is known of Vasti Idulia's beginnings, and most of it is only known through the Dark Jedi's incomplete and corrupted archives, as well as her daughter's research. Although her parentage and birth planet is unknown, and her true name has been called into question, it is believed she was given or left to the Jedi as a very young child due to force sensitivity. She was trained as a Jedi on Coruscant, successfully completing her apprenticeship (although her master is unknown) and remaining on the city planet. It is believed that she was a Jedi ambassador to the senate at one point, which is how she might have met Senator Romulus Lucius (who is, oddly enough, the father of Aalia Ra's second husband, Dominus Lucius). At some point, they became lovers.
Fall to the Dark Side
It's guessed that Vasti and Romulus were involved with each other for quite some time before they ended their relationship, even though the reason for the falling out is unknown. Vasti was assigned to Corellia shortly after, however, and soon became involved with a Jedi there. The only indicator of this is a report in the Jedi archives of the Jedi in question coming forward to report the incident of their romantic affairs. Vasti defected afterward. It is uncertain how she came to know Seraph, but according to the timeline in Vasti's Dark Jedi achive, she became involved under his tutelage shortly after leaving Corellia.
It seems Vasti remained with Seraph and his followers for quite some time, and it is assumed she completed her training under him to become a Jenji'dai. Details of her training, missions and work with Seraph are largely unknown, only that he seemed to highly favor her among his accolytes and collegues. There is also some dispute about her name. Most Dark Jedi replace theirs with a new name after they complete their Dark Jedi training, but Vasti doesn't seem to have followed this practice. This begs the question if Vasti Idulia was her true name before she became a Dark Jedi, even though she is listed under this name in the Jedi records of both Coruscant and Corellia.
While she is listed as one of The Fallen Seven, it's uncertain if it was because she died in action (having been killed by Jedi) or if it was because she betrayed and defected from the Dark Jedi Order; something that was punishable by death and possibly torture.
Regardless, she popped up with the Mandalorians some time later, where there is evidence that she married a warrior of Clan Ra. Whether she was sent by the DJO or Seraph, or if she defected to aid them and the Sith in combating the Jedi, is unknown.
By the time Vasti was with the Mandalorians, she had a young daughter whom she named Aalia. It is assumed that the father was the Corellian Jedi, as the timeline of her giving birth would indicate that she became pregnant while on Corellia. Aalia was obviously adopted by the Mandalorian, as her last name became Ra. With her Mandalorian husband, Vasti had a son named Adan. Despite the children, she and her husband continued to aid the Sith in a war against the Jedi.
It's unknown why, but at some point shortly after Vasti and her husband married they moved to the secluded water planet of Deyer. It was there they raised Aalia and Adan. According to Aalia, her mother, step-father and brother were murdered by Jedi who infiltrated their home. Although Eversio suggested perhaps Vasti was killed by Dark Jedi for defecting and possibly betraying the Dark Jedi Order, it was a notion Aalia rejected, as she had recognized her parents attackers as Jedi.
It should be noted that any information regarding Vasti Idulia has either been corrupted or altered. The reason for this is unknown. The Jedi records and archives, although they seem not to be corrupted, appear changed, although the indicators of the action is very subtle. The timelines of the collective events, for example, seem not to be accounted for properly when held in comparison to each other and to Aalia's age. Aalia's experts could not account for how or why the changes took place.
The Dark Jedi archives, however, are very clearly corrupted, and while it could be because of the course of time, Eversio suggested it was done intentionally. This led him to theorize that Aalia's mother probably betrayed and defected from the order, which could account for Vasti's murders to be Dark Jedi instead of Jedi. Although Aalia agreed that it was odd, she did not agree with Eversio's hypthesis, as she didn't see why those facts would not be accurately recorded by the Dark Jedi, regardless if Vasti defected or not.
As An Alias
Aalia Ra used her mother's name as an alias after the death of her husband and an assassination attempt upon her and her children. It was under this name that she initially became cohorts with Eversio and the Dark Jedi Order, only to shed it again once she was finally assured of her safety.