Official campaign

Official press release

Bards sing tales of heroes from ages past, but never have the Forgotten Realms so desperately needed a champion. Years have passed since the war between Luskan and Neverwinter, almost enough time for the wounds of war to heal. But the brief peace the Realms have known may be at an end. Tension growing between the mighty city-states means the Sword Coast again teeters on the edge of open war. Unnoticed, a greater danger stalks the City of Skilled Hands. Unbeknownst to the denizens of the North, deep in the Mere of Dead Men, dark forces from across the Realms have been rallied under the banner of a legendary evil. If left unchallenged, all of the North is doomed to fall under its power.

Even in this darkest hour, hope remains. A mysterious relic is borne to Neverwinter in the hands of a lone hero so that its secrets may be unlocked - secrets that carry the fate of all the North. So begins an epic tale of shattered alliances, noble acts and dark deeds to be told across the Realms for generations to come.

Pre-release notes

Warning: these are still subject to change during production stage.

General information

NWN2 storyline is set several years after the NWN1 Official Campaign but is not directly connected to it. However, events that happened in the first Official Campaign are acknowledged in-game.
Obsidian has stated that the OC will last approximately 30 to 40 hours and will be enabled for multiplayer. (latest confirmation:C. Avellone for NWN2HQ) It will be broken up into three "acts". [1]
The OC starts with a tutorial about the game. While it may be bypassed, those playing through it will receive "one useful trinket". [2]
At game completion, characters will end up between 15th and 20th level. [3]
There will be two different major endings crafted for both good and evil PCs, as well as a denouement sequence (possibly Fallout-style) that is reactive to many of the decisions players may have made in the game (T. Evans, NWNVault Developer Chat)
PC will be able to acquire and control a stronghold, which will not be class-specific (C. Avellone, for RPGDot)
Overland travel will be handled via the world map, on which player can select known locations in a manner similar to Baldur's Gate 2. Once a location has been selected, the user will travel there – though encounters may happen along the way. (Official FAQ)

Player character

Player can't reuse his/her PC from NWN1 OC and will have to play as a new PC. (F. Baudoin for Shacknews)
In the NWN2 campaign, players will start from level 1, and there will be a level 20 maximum.
Beside choosing class, alignment, abilities and appearance, player will be able to choose from unique backgrounds such as Bully, Farmer, Militiaman, Natural Leader and others. These backgrounds will affect NPCs disposition during initial stages of the game (C. Avellone for TotalVideoGames)
PC's alignment will start as true neutral (except for classes where this would be a prohibited choice: Monk, Paladin, and Warlock) and will shift according to players' in-game choices.(F. Baudoin for Community Update #2) Later information seems to contradict this, so it appears characters can choose any legal alignment to start.
NPCs will react to PC's level of fame, treating PC as a nobody in the beginning of the game and changing that attitude when PC is more well-known. (F. Baudoin for Shacknews)
Character attributes (race, class, ability scores) will affect options in dialog, yet there will be no 'mentally challenged' dialog for PCs with low Intelligence. Bluff/Intimidate is used extensively, as well as Perform and Taunt. Some fights with potentially hostile opponents can be avoided through dialog.(C. Avellone, for RPGDot)

Companions

The player will be able to control a party of up to 3 companions with more than 10 possible companions to choose from. (Atari press-release). Player, if he/she chooses, can walk through most of the game solo, but there are times when having a companion is required (latest confirmation:Papermonk's A-Kon impressions)
Player can take control over companion's actions in battle explicitly, assigning what spells they cast and who they attack.(Atari press-release)
The game will implement an influence system. PC's growing influence over certain companions may cause them to change class and will affect their decision to stay or leave you at key points in the main storyline, as well as other roleplaying possibilities. (Official FAQ )
There will be romantic options available for both genders, yet some of them (if not all) might be unrequited/toned down (C. Avellone, for RPGDot)
Certain companions can back player up with some dialog-related skills and pull PC out of Taunt/Lie failures.(C. Avellone, for RPGDot)
Player won't be able to choose a different class for a companion when they level up. Each companion will have a specific level-up path (e.g. an NPC will always level up in Fighter), except those (rare) cases when player gets sufficient influence over some companions, and could persuade them to change their class via dialog. ( G. Ziets, NWN2 Official forums)

Notable NPCs

Lord Nasher Alagondar will make a return as the ruler of Neverwinter.
Either Aarin Gend, Deekin or Nathyrra will return as cameo/s ( G. Ziets, NWN2 Official forums)
Obsidian stated that four famous Forgotten Realms characters would be in the game, but no avatars of the deities. [4]

Encounters

Encounters in the OC are not automatically scaled to PC's level, but rather manually adjusted by level designers, due to relative linearity of the campaign. (Community Update # 11)
The OC will include a comedic "Battle of the Bards", where PCs can fight against other bards in song. [5]

Locations

Locations include "Githyanki Caves", "Highcliff", and "Crossroad Keep". [6]

Pre-release plot details

Warning: pre-release plot details are subject to change during production stage.

Spoiler warning: Plot and/or ending details follow.

OC starts with the tutorial with PC participating in Annual Harvest Festival, where he/she can try his/her hands in combat, spellcasting and pickpocketing (source: IGN NWN2 video coverage)

PC is possibly an orphan, raised in the village of West Harbor by his elven stepfather/mentor (source: Gamestar.de gameplay footage)

Soon after PC was born, a great (possibly interplanar) war culminated near West Harbour. Current information about conflicting parties is ambiguous, but possible enemies are: Githyanki and certain Sorceror (source: Feargus Urquhart interview to Eurogamer), the King of Shadows and certain Sorceror (source: Atari product page) or any combination of the above.

During the final battle of the war the powerful Githyanki artifact (the Sword of Gith) exploded across the Planes, and one of it's pieces got stuck in PC. Now Githyanki want this piece back. In attempt to recover it from PC's body they attack the village of West Harbour, but villagers manage to drive them off. This sets initial conflict of NWN2 Official Campaign.