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My Faedaen didn't wait for the desired girl in version 1.41. I was just too impatient to install 1.5. After the patch, naturally, I started the Walkthrough over and noticed a difference: all garrisons are visible immediately at the start. Then I noticed another distinction: after reclaiming a garrison captured by the enemy in version 1.41, the ancient ents remained in the garrison, but in 1.5 they joined the hero's army.
In general, the most important resources in this mission are time and money. At the very beginning, I sent a purchased hero without an army on reconnaissance. Then I tried to give Faedaen all the best things the scout discovered. First and foremost—stat boosters. I barely made it. I took the last booster already after Biara appeared. I looked at her army and didn't dare fight her in the open field. Therefore, Faedaen and the hero who was upgrading units in the fort rushed to the Castle as fast as they could. The upgrader arrived first, left the troops in the city, and ran away as fast as he could. Then Faedaen arrived at the castle, where unfortunately Biara found him.