A good expansion that places emphasis on gameplay rather than story.
Storm of Zehir starts either during, or after the first expansion Mask of the Betrayer. As the Sword Coast recovers from the Shadow War featured in the NWN 2 OC, your character and his or her party set out with the infamous Volo on a journey to some place or another. They end up getting shipwrecked outside of Samurach in the jungles of Chult, and some very poor diplomatic talks and combat scenes later you're forced into working for a Merchant company to survive in a land that despises foreigners as a new God strives to make his mark on the realms. That's pretty much the extent of the storyline, sound cool? I'm sure it does, but once you actually see it unfold it's nothing special. I didn't go into Storm of Zehir expecting another Mask of the Betrayer, so I was fine with it. I do think it could have been a little better, though; in some places the plot felt rushed, and it was also very short.
Storm of Zehir focuses mainly on the gameplay, and it does indeed excel in this area. The three new big features are the Overland map, the merchant system, and the customizable party system. The Overland map essentially works like the classic Fallout maps, or those classic JRPG world maps in which you have one character representing your party traveling a semi-detailed landscape to get to their next destination, or simply explore. What makes this Overland map special is that whoever is leading the party determines what encounters you'll be able to discover, or avoid. For example, a ranger with good spot and listening skills will be able to find hidden treasures, and notice hostiles before they notice you. Also a good hide skill will allow your party to avoid hostile encounters. There's also a variety of small dungeons strewn about the overland map giving exploration enthusiasts plenty to see and do. I loved the overland map myself, it made the transition between destinations more smooth than the instant transition in previous Neverwinter Nights titles. Unfortunately the developers decided to add grinding as a necessity to SoZ as well, so you end up battling enemies on the overland map quite frequently in order to gain experience which I found tedious.
The merchant system is somewhat gimmicky, but it's an entertaining distraction. During the Storm of Zehir campaign you gain authority in a merchant company allowing you to establish trade routes, and perform other delightful merchant tasks. It's actually a pretty simplistic system, and if you're looking for a deep business simulator you'll be disappointed. For the most part all you do is establish, and upgrade trade routes by trading gold and certain supplies to establish trading posts in the cities and towns along the Sword Coast. You gain profit from these routes in the form of trading bars which can either be exchanged for gold, or used to upgrade your headquarters at Crossroad Keep. As I said before, it's an entertaining little distraction, but not at all deep and very similar to the rebuilding of Crossroad Keep in the NWN 2 OC.
Finally the party system is different in SoZ as opposed to NWN 2 and MotB. As most should know by now, you create your own party so one should not go into SoZ expecting in depth party interactions. You can pick up to three character's from your NWN 2 local vault and import them into your game at the beginning. Depending on their stats and skills these party members may be able to interject in dialogue with NPCs using the new conversation system which lets you seamlessly switch between which character is speaking to the given NPC. Another nice aspect of the customizable party system is that you're not stuck with the same party throughout the entire game, if you want you can switch out one or more of your members for an entirely different character in your local vault by using guest books at Inns, or the employee registration at your headquarters. The new character's level will automatically be scaled to match yours meaning that you won't have to grind to get him or her up to speed.
Visually NWN 2 isn't any different than the original game, so let's skip ahead to audio. The voice acting isn't that great unfortunately, but I wasn't expecting exceptional voice work in the first place. The music on the other hand is quite good, Storm of Zehir features a very epic and heroic sounding musical score that really fits the mood of the game.
Storm of Zehir is worth playing if you want some great gameplay, and don't mind the absence of an even remotely decent storyline. It's got some great new features to play around with in its campaign, and I for one hope that a talented modder out there adapts the overland map for the NWN 2 OC and Mask of the Betrayer.
Overview:
+Overland Map is great for explorers, and more natural transitions between locations
+Merchant system offers some fresh gameplay to go along with traditional monster slaying
+Ability to completely customize your party, and switch in the middle of a game with no problems
+Musical Score
+Volo
-Weak Storyline
-Short if you don't take the time to explore the Overland map
-Merchant system is simplistic
-MMORPG style grinding