Currently there are 20 quest zones with 1-5 areas within to complete on normal difficulty before the next area unlocks, completing an area will also unlock the next difficulty from Normal to Nightmare
Completing a boss on nightmare difficulty will sometimes yield a unique item examples are, the Shadowknight equipment set, crafting components like the Shield of Ryndor
"If you completed the zones prior to achievements being released then you will have to redo the NM portion of the zone again to get credit. To reset a zone, hold "shift" and click the difficulty tab you want to reset."
Pages in category "Areas"
The following 22 pages are in this category, out of 22 total.