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The key to this mission at the Hero level is to complete it at the beginning without any losses – at least, protect the horses and hellhounds – and most importantly, you don’t need to capture the first Elven castle; the main goal is to capture all the nearby resources and mines (again, without losses) – it is desirable to hire a second hero with luck and level him up even through chests – luck on the road (and there you have your resources). Then, capture the upper-left castle, and then run away from Gilraen for a couple of weeks – get reinforcements from both castles and defeat him. Yes, luck should be at its maximum in battle.