General information
Neverwinter Nights 2 (NWN2) is a PC CRPG game originally released in 2006, developed by Obsidian Entertainment.
It takes place in the Forgotten Realms (the DnD world used in the Baldur's Gate and Icewind Dale series, as well as the original Neverwinter Nights), and uses an adapted version of the 3.5 Edition DnD rules.
NWN2 has a large amount of dialogue and combat, and is said to be better than its predecessor. There are fourteen companions who you may meet at various stages of the game, though no more than five can accompany you at one time. These companions have objectives and personalities of their own, and how you behave will affect their opinion of you. Several of them will initiate friendships and even romances with your character, allowing a great depth of interaction.
You can choose to perform quests in various ways, or even to skip some entirely. Whether you follow the path of good or take an evil road, it will affect how people react to you, and may expand or limit the options available to you.
The game's first expansion, Mask of the Betrayer, was released in October 2007.
Storyline
You begin the game as an orphan living in the small village of West Harbour to the South of Neverwinter. After an attack on the village is defeated, your foster father, Daeghun Farlong sends you to fetch a mysterious silver shard from the nearby swamp, and then sends you to Neverwinter in search of answers.
As you reach the city, you realise that the situation is more complex than you could have ever imagined. You must speak to the wise sage Aldanon, who can hopefully shed some light on the history of the mysterious shard, and perhaps on your own shaded history.
But the more you uncover, the more mysterious the situation becomes...
Modding
Modding is done through the Toolset that ships with the game. While the mods aren't directly compatible, it's possible to open NWN1 mods and extract some of the content to use in NWN2. A number of mods have already been created for the game, and many can be found at Neverwinter Vault.
Links

Mask of the Betrayer (MotB) is the first expansion pack for the Neverwinter Nights II (NWN2) game. You require a copy of the original game to play. You can start the game either with a character who completed the original campaign or with a new character of at least 18th level, though a basic assumption of the game is that you did complete the original campaign.
The story opens almost immediately after the end of the original campaign. Your character awakens in the bottom of a barrow with no idea how you got there and with none of your original companions present. In the course of the game you will explore several areas in the lands of Rashemen and Thay and also visit the Outer Planes. Your enemies include spirit creatures, undead, hags, demons and other creatures. Your companions are fewer in number than in the original NWN2 campaign and are mostly quite unusual, though you will meet one of your companions from the original campaign. In the course of the game your character may reach as high as 30th level.
MotB added rules for characters higher than 20th level to the game. It increased character options with new races and sub-races, two new classes, several new prestige classes, and a variety of new spells and other abilities. Builders have all the new features introduced in the game available to them. All the new material is fully compatible with the original campaign.
