Shallan was a human slave, a lo'taur, in the service of the Goa'uld System Lord Ba'al.
When Jack O'Neill was implanted with a Tok'ra symbiote named Kanan, he was cured of the Ancient's plague, but he was forced by Kanan to rescue Kanan's lover, Shallan. Shallan was a lo'taur, a trusted human servant, in the service of the Goa'uld System Lord Ba'al. She had access to Ba'al's personal chambers, indicating that she was a most trusted servant if not more.
Kanan infiltrated Ba'al's secret fortress where he was working on anti-gravity technology, and used Shallan as an informant by establishing a close, intimate relationship with her. Tok'ra have been known to be a very passionate race and it was not entirely unexpected that Kanan fell in love with Shallan as he gathered his information. After Kanan returned from his mission at Ba'al's fortress, he lost his host and that was when Jack was asked to allow the implantation so that Kanan's information could be reported.
Shallan feared Ba'al. When he saw that she was the object of the Tok'ra's attention in a rescue attempt, he placed her in a holding cell. Jack was able to escape the fortress and he rescued Shallan from certain death. In gratitude, she decided to stay with the Tok'ra and fight in Kanan's name. It is not clear whether or not she was willing to become a Tok'ra host, but the idea was probably not new to her since she had been in service to a Goa'uld and was most likely trained with that possibility in mind.
--DeeKayP 18:33, 6 Jul 2004 (PDT)