Yes I know how you can feel entering the castle -.-, but it is like a Level 6 in the game
To beat the other 3 dungeons, or at least to get the item, its enough with your current sword
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EDIT: I made a update. Sorry, hope this is the last! It should be available soon
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Tried to find more supers but I have limited access of the mines without the Mine Cart. Same with the Dark Forest. Where is the mine cart? And the Bowless Blue Mail since the Bow requires a key?