I think AERITH means Heart , and last words related to Bastesh , a place on Issavi where the goddes of the undersea lives , there are some books that talks about this. You can found it on the library of Issavi.
Also in test server there was some stairs to underwater on Issavi that after the test server got dissapeared. And there was some stories about a character that hides underwater.
"Finally, Uman united with Sula, the sea, and that was the hour that Bastesh the Mistress of the Sea was conceived. She was exceedingly beautiful, and Uman and Fardos were sad when they saw her, for she reminded them of Tibiasula, Bastesh's divine ancestress. But alas! Her beauty would not last. When Fafnar, the vain sun goddess, beheld Bastesh, she exploded with jealousy and attacked her with all the fury of her injured pride. Deep sank her fiery claws into the frail body of the newly born goddess, and had it not been for the other gods she would have torn her apart. That was the moment Suon decided to punish his sister for her misdeeds, and as a just punishment she was sentenced to continue her flight eternally, fleeing across Tibia's skies from her brother's fury. Bastesh, however, never fully recovered from the terrible wounds inflicted on her by her jealous cousin. Her beauty was ruined forever almost as soon as it came to this world, but worse still were the scars she bore inside. She grew up to be shy and melancholic, preferring the quiet solitude of the ocean whose waters are said to be salty because of her ceaseless tears. However, even though she rarely communicated with the outside world her presence was revealed by an abundance of sea creatures that soon came to populate the ocean." Text from book on Issavi
*Galthen went to Isaavi and he went missing according to Spectulus" Another hint we can find on Spectulus info.