BioWare designed Neverwinter Nights such that making user-generated content for it is much possible, given enough determination and imagination on the part of the user to use the sophisticated tools. It is this wise decision that ensured the game would still be played for years to come.
However, the technology that powers the game's creation tools is not as good at powering the game's graphics, which were already rather dated even during the time of the original's release.
The latest official expansion will not give impressions that are different from the above. In fact, a sceptic would be more than convinced that Neverwinter Nights is becoming more of a fossil, visually. After all, it would be apparent to an industry-watcher that any improvements that BioWare has made over the Aurora engine were not implemented to the engine that the customer obtained (thus depriving the customer of added-value), but rather have them repackaged with new names and new patents (such as those used for BioWare's other games, such as Knights of the Old Republic).
The premise in Hordes of the Underdark is yet another struggle against ancient, enduring evils that had been unleashed upon the similarly enduring lands of the Sword Coast, which is the usual setting for Dungeons & Dragons stories set in the world of Toril.
The player character is the protagonist from an earlier expansion, Shadows of Undrentide, which ended in a convenient cliffhanger that left the player with no knowledge of the player character's whereabouts, other than the player character having been thrown into another plane of existence, albeit a very mysterious one. This gives BioWare an excuse to implement a deus ex machina, which would not seem so unbelievable considering the ties that Dungeons & Dragons has with an even more otherworldly setting, Planescape.
The protagonist is of course saved from an ignominious fate of drifting in a dark, dark plane for all eternity, but is now in possession of a trinket that would prove to be more trouble than it seems.
Lured by promises of great adventure and/or riches/fame (the player gets to decide in conversations with NPCs – not that such motivations would matter in the long run), he/she has travelled to the grand city of Waterdeep to partake in yet another expedition into Undermountain, the vast dungeon underneath Waterdeep that promise wealth and death in equal measure. Of course, as is typical of a BioWare story, things go awry early on, giving the player a more gripping impetus than just another quest for riches and renown.
Before starting the adventure proper, the player is given the choice of creating a player character from scratch, or importing one from previous games. There are a few new races to use, though these would be quite familiar to Dungeons & Dragons veterans by then. Importing is a matter of converting characters made using the systems in earlier expansions or the original package; this is virtually glitch-free, thankfully. In either case, the player character will be close to level 20 or higher (in the case of imported characters), because Hordes of Underdark happens to have settings that would be lethal to the novice adventurer.
If a player that has played the earlier Neverwinter Nights games starts a new player character for any reason, he/she may notice that some existing feats and skills have been tweaked, to accommodate the new ones.
The new feats would be familiar to veterans of Dungeons & Dragons rules, edition 3.5 of which allowed for characters of so-called "epic" levels. Many existing feats have "Epic" upgrades that can be purchased for even greater bonuses; the player would be wise to consider these, as the challenges ahead can throw a lot of nasty numbers at the player.
The completely new feats are associated with the new prestige classes, and these are perhaps some of the more exciting appeals of the expansion. As in Shadows of Undrentide, fulfilling characteristic requirements that reflect the personalities and inclinations of these prestige classes allows a player character to invest in levels of these powerful and esoteric classes.
One of the new ones is the Weaponmaster, who can be potentially overpowered if given the right magical weapon. While the Weaponmaster may only focus on the use of just one single weapon type, which can be a problem if a combat situation simply does not favour it, the bonuses that he/she gets in using that weapon are so tremendous that in any other situation, he/she would butchering through the opposition.
The same can also be said about the other prestige classes, especially the spell-casters as they still benefit from the convenient resting mechanic (though this does have more risks now, such as monsters appearing out of thin air to attack the party if the player made a bad roll). However, the player can also expect the opposition to have such characters too, so blunders and careless mistakes are still costly, or at least embarrassing.
It is worth noting here that unlike Shadows of Undrentide, the player can continue to invest in prestige classes beyond level 10. While the player character does not gain any new abilities beyond level 10, the existing ones still benefit from a higher level in these classes.
Of course, a player may choose to multi-class anyway for added versatility, so this is where the game reminds the player through tips and hints in loading screens that while a jack of all trades is more versatile indeed, the Hordes of the Underdark campaign is better played with a specialized character, which would have statistics that are high enough to survive and overcome the challenges of the campaign.
Most of these prestige classes do not look any more different from those of the fundamental classes. Those that are the exceptions, however, only serve to highlight the aging graphics of Neverwinter Nights. One of these is the Red Dragon Disciple, a prestige class that emulates some of the characteristics of the fabled Red Dragon, including its wings. Wings will sprout out of the character's back; while these wings are well animated, they are ultimately vestigial and only there for cosmetic purposes, and even these they do not fulfill well, due to the awkward attachment of the wing polygons to the rest of the character's model.
Going together with these new options for advancement of player characters are a slew of new properties for items. A notable handful of these can only be used by the new prestige classes, hence further encouraging the adoption of the prestige classes.
Otherwise, the new item properties are not additions to the base library of item properties, but rather script-dependent items that can only work in the Hordes of the Underdark campaign, meaning that they just won't work right in other campaigns. A very good example of this is a certain magical blade that also doubles as an NPC, and whose properties have to be altered by going into a conversation with this NPC. While conversing with this NPC is not an uncomfortable experience, it is however a bit tedious.
To match the challenges that the player would face, many of the weapons and armor in this game have bonuses beyond the "+5" rank (which is a term that Dungeons & Dragons veterans would know all too well as the rule designers' conventions on grading the power of such items). The Hordes of the Underdark campaign also has an NPC that allows the player to upgrade existing weapons to dizzying heights of power, possibly giving weapon-using classes a rather distinct advantage over spell-casters, especially when dealing with enemies of garbage quality.
When dealing with very powerful enemies – and a lot of them, as the game would throw them at the player often – spells may be more efficient and effective at getting rid of them. The new spells in Hordes of the Underdark are frighteningly powerful, capable of inflicting both damage and debuffs at the same time. New spell feats, including the Epic upgrades, make them even more fearsome to use.
The graphical effects of some of the new spells appear to have been recycled from existing ones, which can be a bit disappointing. There are some with their own unique animations though, so they are not all rehashes.
Although BioWare's games generally did not push the boundaries of technology during the time of this game and before it, the main appeals of BioWare's games were their story-writing and choices for voice-over talents. Hordes of the Underdark is no exception.
Although the player character is still a disappointing mute, other major characters in the game are fully voiced. BioWare can do little about the lack of facial animations and lip-synching that has been in the game since the original, but listening to their voice-overs is plenty entertaining enough to distract most players from this visual blemish. One of the notable voice talents is Caroline Livingstone, who would go on to give more voice-overs to future BioWare games and even become the voice directors of some.
Then, of course, there is Deekin, who still retains his love-him-or-hate-him qualities. As usual, Deekin is the source of comic relief and has at least one conversation topic with every other major character in the game, which generally has him unwittingly annoying or amusing the heck out of the latter.
The pace of the story is as to be expected from a BioWare game. The overarching plot will eventually change and escalate into something more serious, which is typically about the fate of the world of Toril, as usual. There is the usual conspicuous but not overbearing melodrama that emphasizes the brevity of plot twists, as well as a fitting finale that has the player doing things that a mortal in the Dungeons & Dragons universe would never have dreamed of doing. To elaborate this would be to invite spoilers, but generally, the player will be crossing through a lot of dimensions that would be familiar to those well-versed in the Planescape settings of Dungeons & Dragons and defeating a lot of extra-planar creatures, many of which have their own models.
However, there are still disappointments to be had with the story direction and execution. The most apparent of these are the level designs, which are unfortunately marred by the limitations of the dated Aurora engine. There are a lot of recycled terrain and textures, such that it would be difficult to differentiate one of the Nine Hells of the Baa'tezu from the frigid region of Toril that is Icewind Dale. Furthermore, while there are new models for certain creatures such as the Illithids (a.k.a. mind-flayers), many other creatures are given models recycled from existing ones, or are even recycled from the new ones. Of course, BioWare still tries to implement some graphical effects to accentuate the themes of these environments and creatures, but it ultimately has very limited tools to work with.
The other major disappointment is how BioWare reintroduces some companions from the original Neverwinter Nights in the early parts of the campaign, and then takes them away in the next part and replaces them with merely two (plus one, if Deekin makes it to the next chapter). There would have been potentially intriguing entertainment to be had from learning how these companions had changed since the original campaign, but the player is given so little opportunity to explore these secondary plot-lines before they are permanently separated from the player character and completely forgotten by the time of the end of the game.
Sound-wise, the game's sound effects are mostly disappointing rehashes of existing ones. This was a problem in the original game and the previous expansion, so it is all the more disappointing that BioWare had not seen fit to compose and include more fresh sound effects.
The soundtracks are much better done though. There are some new tracks that better accentuate the otherworldly places that the player will go to, and most of them sound fittingly ominous and foreboding.
As in the previous expansion, the Aurora toolkit has been expanded with new scripts and tools, the better for the ardent fans of Neverwinter Nights to craft new user-created adventures or improve existing ones with. This is perhaps the best value of this expansion. The computer requirements for the Aurora toolkit have not changed by much though, so a powerful computer is still required to run the entirety of the toolkit with satisfactory speed.
In conclusion, one should not expect Hordes of the Underdark to alleviate Neverwinter Nights' greatest drawback that is its very dated graphics technology. However, in terms of new content, the expansion certainly does deliver a lot, as well as an epic finale for its official campaign.