The level limit is 11. I think this could be increased. The reason for this is that the very large camps like the ones with the Orc Overlord and the Goblin Overseer can defeat the party not easily, but regularly. I can finish most things with ease at this point without losing brothers. I am playing on normal. I am finding it not hard to deal with the withered vampires.
I think there should be a point every level. Maybe there should be access to better unique weapons at level 11+ from defeating enemies. I found a few unique items mainly on bandits and skeletons. There are occassional better shields from undead as well as swords. Some of the higher level orc items are interesting.
I think at level 10, there should be quests and encounters for parties that are unique, then level 11, then level 12. This would be a good point to add a story line because most of the map will be finished by then. Maybe, the lords will find the characters worthy then.
Also maybe instead of giving additional points, there might be perk quests which give titles or unique perks to level 11+ characters. Go hunt the dragon, find the hidden philosophers stone, etc.
This would be a good point to create access to easter eggs, unique terrain encounters.
It also might be when some of the towns ask your characters to go into the unexplored areas of the maps with orc, goblin, and undead cities. All of the encounters initially are near the towns. There are no travelling quests in the game yet.
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