Tower tactics.

I've already tried it. Now the situation is different. Siila, with her slow troops, ran so far, destroying 2-3 blocks, that the fast-moving supposed main hero (specializing in physics) couldn't catch her and didn't manage to fight a single battle in the first 2 days.

Move the army in a chain from one front to another. If Ciel has run somewhere, maybe the main hero should go in the other direction? A typical tactic is for the hero to reach a secondary town, capture it, find a tavern there, buy another hero, and this hero returns the army to another front.