Grover’s Expedition

Thank you for the hint. It was difficult to figure out, as it was with the fact that you can’t use the tear in the city (all of this should have been mentioned). And now, about something sad. Nibros is, of course, a cheater (a fan of dark magic), but we are winning. I switched from Chaos to Light and took the corresponding tome. As a result, with the help of Haste and Retribution (and when necessary, Dispel), I defeated all his troops. But here's the problem: the battle didn't end there; he casts spells without troops. I'm seeing this for the first time. How should I understand this?