Fayden stands in the capital and focuses solely on defense. Using a mercenary, we free both heroes, and the order doesn't matter much. We level up Talannar and Dirael on every encounter. My mercenary stood near the factory and exchanged resources. When a sufficient army is gathered in the capital, we take the freed hero (in my case, Talannar) and those who are not participating in the defense (i.e., unicorns, dancing with death, fairies, part of the ents) and go to destroy the Necropolis castle. After a glorious victory, we return to CyrisTalla and give the troops to Fayden. The tasks are completed. P.S. Thanks to Alan for the saves, but I didn't use them.