The dwarves, in turn, are bound to one of the clans of Grimheim by a pact, according to which the latter is obliged to provide military support in the capture of all the fortresses of the Fortress faction, or all the cities of the Sylvan faction, with an adjustment for the alliance.
Added 10 minutes later
The low difficulty level in the fourth mission can only be achieved by helping the Empire's troops in the southwest corner of the map defeat the undead.