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I completed the campaign for Queen Lamanda in 110 days, and I had to redo many sections to optimize the main hero's moves and replay battles.
The first level is completed in 3 days.
And yes, I took all the chests for money, quickly built dragons, and arrived at the enemies' locations early. Usually, 4 dragons with reinforcements were enough, except for the level where I had to defeat the warlock in the volcano, which required 7 dragons, 4 phoenixes, and reinforcements.
In all levels, the main hero was a barbarian, sometimes a knight if the terrain was suitable. I only bought the spellbook at the very end of each level and used only level 1 magic because there wasn't enough time to build level 2.
Attached are the save files for levels 5-8 before the final battles. On levels 8 and, especially, 7, I had to replay the battles many times to achieve victory. The setup is already suitable; you just need to make the right moves. Morale and luck also have an impact, but not as much as the correct moves and surviving units.