Step outside (bring henchmen/your party too!), and just follow the 模板:Heroes of Ascalon (德佛娜, 莘 and 涵洛) on the short walk to a nearby cliff that allows for a close view at the 岩山. On the way there will be quite a few 三頭龍s, just kill them and move on. The leaders of the party walk quite slow and seem quite aggressive towards any Hydra they see. Also, they can get killed and it won't affect the outcome of your meeting on the top of the mesa.