Athorton was a young sage in the early 1200s DR.
By the mid–14th century DR, it was theorized that it was Athorton who stole the Tome of Torment—the holiest book of the faith of Ilmater—from the priestess of Loviatar, Lalaskra of Ormpetarr. Lalaskra had worn the hairshirt tome constantly, but removed it during a ritual in the Year of the Crimson Crag, 1211 DR when it was stolen by an unknown thief, who also managed to make off with the tome's covers, stored in a backroom in Lalaskra's quarters in a nearby temple. Incensed, Lalaskra whipped her Loviatan minions into a frantic search for the Tome all across the southern Vilhon Reach lands, though without success.
In later years, Athorton wrote extensively of the magic of the Ilmatari—magic known to few outsiders and widely mocked—and he may have acquired such knowledge via the Tome. As an old man, he became friends with Beromchess Ilthyn, a local priestess of Ilmater. Following Athorton's death in the Year of the Shattered Altar, 1264 DR, Beromchess covertly took the Tome to the House of Holy Suffering in Mussum.