According to Hod, the Balaur can attack Beluslan because the Observatory had been destroyed. So the Observatory must be rebuilt in order to weaken their power. The soul of the Gwendolin, protector of the Aetheric Field, is supposed to be somewhere near the shattered Observatory. You should meet with him and find out how the Observatory can be rebuilt. Gwendolin told you that he couldn't find any rest until the Balaur had been driven out and the Observatory had been rebuilt. He asked you to go to Reshanta, as strong Aether energy will be required. You were able to gather Aether with the help of Hisui at the Primum Landing and Glati in Krakon's Dispute. You returned, drove out the Balaur and rebuilt the Observatory.