There you will find Nekarat the Keywarden and a slew of elite mobs. If you still need a stack or two of Nephalem Valor but run into Nekarat first, run away and seek out an elite mob. Thankfully, Keywardens will not pursue you very far.
Before you can even begin to think about crafting a Hellfire Ring, you’re going to need an Infernal Machine. Crafted by the Blacksmith, Infernal Machines will allow you to access one of three portals. Inside each portal resides a pair of Uber bosses. Buy Diablo 3 Gold Defeat these bosses and there’s a chance that they’ll drop one of the Hellfire Ring components. But first, you’ll need the Blacksmithing Plans for the Infernal Machine.
Change your quest to the “Prime Evil” and head to Act IV. First, we’re going to need five stacks of Nephalem Valor, as the Keywarden will never drop the plans unless you have them.
Your best bet is to clear the Gardens of Hope Tier 1 for 1-2 elites first, and then head to the Gardens of Hope Tier 2 for 2-3 more. If you do not have five stacks by then, don’t worry about it. Port back to town and take the waypoint to the Crystal Colonnade. From there, travel to the Silver Spire Level 1.