NOTE: To get into the mine, throw a dagger at the gold lock!
Apologies, but I forgot to add the dialogue to the blacksmith to give you that hint.
Also, once you get to the Jump Boots, and the Goblin worship song to Grunthusk, Necromancer God that's as far as the game goes. You can go back and gather more heart pieces with the boots, but I didn't get to develop the second and third set of levels I had planned.