Things You'll Need
Instructions
The Upgrade Process
Defeat Baal, the final boss monster of Act V who is located in the Throne of Destruction in Harrogath. You will be upgraded immediately to the next difficulty level. From Normal difficulty, you will be upgraded to Nightmare, and from Nightmare, you will be upgraded to Hell. In each of the sequential difficulties, you will face enemies whose weakest varieties are stronger than anything from the previous act. Naturally, you will need to increase the strength of your character dramatically before proceeding to the next difficulty level. The easiest way to do this is by upgrading all of your equipment to the next tier.
Now that you have determined you need to upgrade your equipment, you will need to obtain the items necessary to do so. Be sure to do your Hellforge quest, located in Act IV. Smashing Mephisto's Soulstone on the Hellforge drops High Runes, such as Lem and Ko, as well as several perfect gems. You will also need the Horadric Cube, which you should have obtained in the Halls of the Dead of Act II. Perfect gems and High Runes can also be obtained by combining three lesser components in the Horadric Cube. For example, three chipped Emeralds combined in the Cube will garner you a flawed Emerald, or three El Runes will yield a Tir.
Upgrading your gear is different depending on the rarity and type of the equipment. For Elite weapons, place the weapon to be upgraded inside of the Horadric Cube, along with a Fal Rune, an Um Rune and a perfect Sapphire. For Exceptional weapons, place an Ort Rune, a Tal Rune and a perfect Sapphire. For Elite and Exceptional armor, place a Pul Rune, a Ko Rune and a perfect Amethyst. Using the Horadric Cube with any of these recipes inside will yield the next tier of equipment --- normal gear will upgrade to Exceptional, and Exceptional will upgrade to Elite.