Maybe later on companions? or more objectives in the dungeon, like saving an NPC or something.

I would pay money for this, great job. I think the idea of an overworld and NPCs is great. maybe you could sell your treasures, or have an NPC identify your potions for you. As for the leveling system, I think you should make Level ups happen less often, and have the first dungeon be short and fairly easy. Then every dungeon you do gets progressively harder and longer.
 
   Some other things I have noticed is that delver's footsteps sound the same on all surfaces. It would be small, but cool if every texture he walks on has a different sound. Also, by holding both W and either A or D, I was able to move much faster. I don't know if that is supposed to be like that, but it allowed me to escape very quickly and easily.

    Keep up the nice work!