Underground Gallery
To simplify the explanation just a little, I have incorporated a map system.

This is a map of the next section. The path to the boss is marked in yellow. Follow that path if you want to just beat the boss. To get all of the extra items along the way, take the lavender path. The gray areas are hidden rooms. You must strike the wall with your whip to access them. The red dots are Heart Max upgrades. The orange items are Health Max upgrades. The light blue items are Magic Max upgrades. You can only get the upgrades that have lavender lines going to them. The other ones you will need more Magic Items to get to. The red squares are save points. Always save your game at a save point. Not only can you save your game but you can also replenish 100% of your health and magic. Be aware that I will not tell you to level up. It will be your responsibility to do so. I will also not remind you to go back and grab any extra items that you may have missed. You can stray from this guide at any time to get extra items you missed.

Alright, this one is going to be easy. Follow the yellow line to the first save room, grabbing the extra item on the way. Save your game and continue following the yellow line. Grab the two extra items you come across and continue to the next save room. Save your game and head to the boss. Beat him and grab the Heavy Ring. Head back to the save room and save your game. At this time, you can go back to the beginning of this area and grab the two extra items you passed by, now that you have the Heavy Ring. After that, head to the second save room, save and grab the last two extra items. Now, you may be wondering how to cross the falling bridges. The first bridge, just run across and slide through the narrow passage. For the second one, you need to start running in the previous screen. That's it. Now head to the leftmost end of this section.