Hades

Hades
Hades is an area at the bottom of the world. If you're going to go down here then you will want some obsidian skin potions or an obsidian skull. This is the only area to obtain Hellstone and lava. It is also home to the Wall of flesh. The only way to unlock Hardmode is to beat the wall of flesh which can only be fought here so you have to come down here at least once to unlock hardmode.

Tips

 * Only go down here if you are properly prepared. An unprepared player can fall down into a pit of lava the moment he/she enters