Once Kethrendil has ensured that Haspur is in a secure and comfortable place to rest, perhaps a room inside the Gondite temple, he go to see that G'axir's body is taken care of. After doing, he will seek out someone to bring some messages to Evereska, hopefully a fellow elf. He will prepare two messages. One addressed to the Hill Council, detailing everything he had learned about what happened to the gods, the Weave, and everything he knows about the coming enemy and their advanced technology. He implores them to find secure refuges for the People, to help find a way to repair the Weave, and to work together with the other cities of the Heartlands in preparing to fight the Dragon Empire.
His second letter is addressed to his family, House Symbaern on Evermeet. He hopes that it can be brought to the island through Evereska. In it is much of the same details as the first letter, and he implores his family to bring this information to Queen Amlaruil and her advisors. He also adds that he will remain on the mainland, saying only that he is on a mission that may be a key part in repairing the Weave. If need be, his family could contact him at Baldur's Gate or Candlekeep.
After that, he start preparing for the trip to Candlekeep, seeing if he can get a carriage and getting supplies, and planning the route.
