Necromancer – “Ruler of Erathia” [Campaign 3, Mission 5]

I just can't seem to turn people into undead, even though I have the corresponding structure built in the Necropolis castle! Maybe I haven't learned a certain spell? I don't want to replay the entire Necromancer campaign again, I've already replayed it once to develop my magic skills for "Mind Lord," but I still haven't learned how to sway Titans or anyone else to my side... People, please don't get angry, just tell me what the mistake is? Added after 3 minutes And I still don't understand what the point of dragons is. Godric sits in the castle behind the walls, and the dragons just die from the attacks of mages and others... Added after 1 hour 15 minutes I did it! First, I infected everyone with the plague (in three turns), and then I just raised the dead, and that's it... After defeating all the mages and genies with the Titans (they died on their own turns little by little), Godric had a "human" army, and I infected them with the plague too... Before starting the "Warlock" campaign, I'll read all the posts about all the missions, and then I'll start!