User blog comment:NickTheStick248/Talkin & Walkin/@comment-5014408-20120523000343

The Underworld's a fun place to hang out!

Good armor is not completely necessary, you can always build stone walls around yourself and deflect Fire Imp projectiles with a sword. A good weapon is very necessary, Blade of Grass worked well for me. A Muramasa, if you've ventured into the dungeon, will be a good idea. Obsidian Skull, Horseshoe or Shield are a must for hellstone protection. Some Obsidian Skin Potions for lava protection wouldn't be a bad idea either.. Some things you can do there:

-Mine Hellstone! Hellstone makes Molten Armor, the highest tier pre-hardmode armor, and some very good weapons such as the Fiery Greatsword, an ingredient in the Night's Edge.

-Farm Demons for the Demon Scythe spell, a very useful spell pre- and even after hardmode. You can also farm Fire Imps for the extremely rare Plumber's Hat.

-Grab some Ash Blocks for a Fireblossom farm or iridescent bricks.

-Funnel part of the Ocean down there for lots of obsidian, but make sure it isn't too much since water evaporates in the Underworld.

-Make sure to steal a Hellforge from one of the houses, for Hellstone Bars.

-If you have a Shadown Key from the dungeon, you can get some very nice weapons from the Shadow Chests down there.

-Make a nice long flat surface, in preparation for a Wall of Flesh battle.

Have fun!