My theory is that Tuon is collard with an a’dam and held in the “Towers of Midnight” (The “Towers of Midnight” are clearly identified in the guide as being in the city of Imfaral (the sixth largest city in Seanchan). The ToM are also mentioned in the TGH (See the WOT Encylopaedia)) by dark channelers (BA or a Forsaken) while 13 Fades and 13 BA are gathered to in an attempt to replace the The Great Lord’s control of the Seanchan, that was lost with the failure of Suroth.

This would allow Tuon to experience the abomination that is the Damane/Sul’dam system, and finally break her of her belief that that collaring a woman that can channel is OK. If Rand is involved in her rescue, it would put them both in the right geographical location for him to bow to the Crystal Throne, and Tuon in turn to bow to the Dragon Reborn, thus fulfilling both of the Karaethon Cycle Prophecies “He "shall bind the nine moons to serve him" and "The Dragon Reborn must kneel before the Crystal Throne before Tarmon Gai'don, or all is lost."