Collect all sixty Poe Souls around the game and bring them to Jovani inside the house on the southeast corner of Castle Town. Become a wolf and dig your way into the house. Give him the 60 Poe Souls to receive unlimited rupees. Now go into Kakariko Village’s Malo Mart and donate enough money so the prices at Castle Town’s Malo Mart go down. You should now be able to buy a Magic Armor for 598 rupees. Normally having the Magic Armor on reduces your rupees, but since you have unlimited rupees you will stay invulnerable to damage for as long as you want.