Dathana was a mage who lived in Kethsi at an unspecified time in the past. She is not seen ingame, and presumed to be (like the rest of Kethsi) long dead, though a message written by her is found during Ritual of the Mahjarrat. There she details the Kethsians' discovery of the Stone of Jas by Etheron, an Elder Mage in the Mage Conclave of Kethsi (of which Dathana was also a member).
She goes on to note that the Stone was a powerful artefact which, when taken to Mount Firewake, helped the Kethsians prosper for several months by aiding with harvests and the like. Unbeknownst to the Kethsians, the Dragonkin grew angry at others' use of the Stone of Jas and invaded Kethsi from the east, ripping apart and destroying the plane as an act of revenge.
Dathana was part of a small group of mages in the Conclave which fled to the Isle of Sann, where they began to use the rare bane ore on Kethsi's tempered anvils to combat the Dragonkin. Their efforts were ultimately in vain, however, when their supplies of bane ore ran low. It is not specifically stated what happened to Dathana or the other Kethsians, but when the player visits Kethsi during the Ritual of the Mahjarrat quest, they find the plane in ruins, no living thing having survived.