There is no need to do any of the fjords before getting the battle tower, though you can level there a bit (which makes the first dragon battle easier) and pick up an extra dragon skill point (I put one in Dragon Spirit and one in Fire Sphere). There is a barrier blocking off most of the fjords, that you need to be able to transform into dragon in order to disable.
There are a couple pieces of dragon armour in your battle tower chest.
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