The only difficulty on the map is Rosalía, with her magic and decent army. After successfully eliminating her, only Eduardo remains, who runs along the same route to the central fort once a week, with a one-week replenishment.
To successfully eliminate Rosalía, you first need to take the upper human castle – get vampires for it – use the vampires to capture the artifact shop – get liches for the shop – have vampire and lich upgrades in the castle.
Also, regardless of the preferred path (Blood/Tears), it is worth gaining 100 reputation of each type (the additional quests give very good bonuses). Blood's priority is +1 spider growth and +5 magic power.
The maximum level on the map is 20, so it is worth visiting the library immediately after level 11+ for the maximum bonus.