Tia is the mysterious twin sister of Orlha. After their birth, their parents believed the El Nido superstition that twins are a tragedy, and their mother took Tia away from Orlha and her father. Tia fell into a coma around 1020 A.D. in Home World and could not be woken. Eventually, Orlha came with Serge and visited her; Tia mentioned that she was grateful to have finally met her sister, and noted that her spirit would always be with Orlha. She then passed on to death; Orlha lamented her fate, though Tia soon reappeared and comforted Orlha, allowing her to learn her final technique, SisterHoods. The technique summoned Tia to attack with Orlha in an offensive. Tia also gave Orlha her piece of the Sapphire Brooch, allowing it to become a Blue Brooch.
Tia's language at the meeting is a little mystical, and possibly suggests that the two twin sisters never met before Orlha crossed the dimensions to Home World. There's a theory that Tia was duplicated from Orlha when the dimensions split, but retained her own identity. Most likely, Tia simply had already died in Another World, while Orlha's Home World counterpart was no longer in El Nido.