Multiplayer (MP) means having more than one person playing in a module at the same time. The original campaign, Shadows of Undrentide campaign, some premium modules (specifically, Witch's Wake, Pirates of the Sword Coast, and Infinite Dungeons) and many free modules from Neverwinter Vault are suitable for this type of play. The Hordes of the Underdark campaign and the other premium modules (ShadowGuard, Kingmaker, and Wyvern Crown of Cormyr) however, are not intended for multiplayer gaming (although the Hordes campaign can be made somewhat multiplayer friendly, see the Campaign Multiplayer Workaround Thread in BioWare's forums — may contain spoilers). Multiplayer can be run over the Internet or locally over a LAN.
There are no monthly fees associated with playing Neverwinter Nights as a multiplayer game. Neither BioWare nor Atari charges such a fee, and it is illegal for anyone else to charge for playing the game. (Even "perks" given in exchange for "donations" run afoul of the EULA.)
Each multiplayer game has a host (often a player) who runs the server for the game. Servers can be linked through portals, allowing players to travel between the two worlds simply by stepping through the portal.
There are several types of multiplayer games played. The basic type is played essentially the same as single-player, but with multiple player characters involved. A more traditional Dungeons & Dragons feel can be obtained if one (or more) of the players assumes the Dungeon Master (DM) role, allowing the other players to be more creative in their strategies. (In fact, some modules are designed for open play, requiring a DM to make the game proceed as intended.) This is the type of play typically meant when players refer to "multiplayer campaigns" or "multiplayer groups" (or sometimes even just "multiplayer", even though that lacks precision). This is also the type of multiplayer that is officially supported.
Another type of multiplayer games are the persistent worlds, modules hosted at all hours, so players can log in and play whenever desired. Rather than presenting a fixed story line (as in most single-player modules), persistent worlds tend to focus more on providing a setting, giving players the option to proceed in whatever direction they desire. Some persistent worlds are story-based, but more common are the ones that rely on players to improvise their own stories, possibly with DM assistance. While this type of multiplayer has been intentionally made available as an option, it has not been officially supported (meaning that issues affecting only persistent worlds have been given a low priority by the official game support).
All of these types of games differ from other popular online games in that they are not "massively" multiplayer. The approach taken with Neverwinter Nights is to mirror the pen-and-paper model of role-playing. The intent is to support a group of friends getting together and playing through a great story, possibly with a Dungeon Master to moderate the game play. The party-based adventuring experiences in massively multiplayer games have been placed in the context of a gripping and immersive story line in which the players can be full and important participants. The goal is to blend the best of single-player and massively multiplayer games, as well as the classic experience of pen-and-paper role-playing, to create the best of all possible worlds.
Multiplayer games can be classified by the permissiveness of player vs. player (PvP) combat. The host will determine the PvP setting of the server, which is broadcast to anyone attempting to join. The possible settings are "full", where all players can be potential targets, "party", where players cannot target other players in their party, and "no", where PvP combat is banned altogether. It is also possible for the PvP setting to become more restrictive on a per-area basis within the module. Bioware was very aware of both the positive and negative aspects that can emerge from player vs. player combat in an online game, and therefore put a lot of thought into this issue. While this setting was originally intended to reveal the permissiveness of PvP combat, it is also used by some servers merely to mimic a harder difficulty setting and increase the challenge (as under the more permissive settings, a player can accidentally injure friends with a misplaced spell).
A distinction can be made between cooperative and competitive multiplayer. In particular, intentional PvP combat and player killing (PK) may be allowed in some games, but not in others. Games that allow PK necessarily must have a "party" or "full" PvP setting, but the converse is not true – servers with a "full" PvP setting may still prohibit intentional PK, particularly if it could be considered griefing. These restrictions are not automatically broadcast to players seeking to join a game, although some servers will mention PK in the server or module description. There are servers devoted to intentional PvP combat, perhaps most notably the servers classified as "arena" servers.
A multiplayer game is hosted by one player, often either the DM or the player with the fastest computer. In any event, the host is the (only) one who needs to have the module being played, so this role may fall to the module creator, regardless of other considerations. Hosting can be accomplished with the dedicated server or by going to the "Multiplayer" section and clicking either "New Internet/LAN Game" or "Load Internet/LAN Game" (the latter for loading saved games in multiplayer mode). These options bring up screens similar to their single-player counterparts, but there are several additional options available, such as giving the server a name or establishing a password for other players joining the game.
Other players join the game by starting their clients and either selecting the server from a list or entering an IP address for a direct connection. The server lists are obtained by going to the "Multiplayer" section and clicking either "Join Internet Game" (for games hosted over the internet) or "Join LAN Game" (for games hosted locally, such as over a home network). Originally, there were lists, broken into various categories, of all active Internet servers that opted to be listed via GameSpy. However, GameSpy no longer provides this service, leaving only the "history", "favorites", and LAN lists.
When entering the multiplayer section of Neverwinter Nights, a player will be asked for a user name and password. These are authenticated by BioWare's master server, if that server is available. If the master server is not available, then these can be anything, provided each player chooses a different name. (The master server has never been available for a LAN game with no Internet connection.) User names are case-sensitive and are used by the server to prevent one player from taking over the characters of another.
The master server has been completely unavailable since the summer of 2011. Consequentially, some servers have taken additional measures to verify the identity of players. These measures are server-specific, but often are unseen by players using the same computer each time they log in. In other cases, players may need to contact the individual server's administrator(s) to learn about the security measures.
Playing Neverwinter Nights in multiplayer mode is very similar to playing in single-player mode. The story of a given module does not change, but there are a number of automated features to help balance the game, including the dynamic scaling of combat encounters according the size and relative strength of the party.
One difference is that players can go exploring by themselves, whereas computer-controlled associates will always follow their master through area transitions. BioWare feels that this freedom is very important in a multiplayer roleplaying game, and the official campaign was designed with this in mind. It is possible, however, for other modules to designate an area transition as "party-required". This will require the entire party to assemble near the transition and cross it together.
The information given to players about others' player characters is fairly limited. Neverwinter Nights is all about role-playing; what is on a player's character sheet is between that player and the DM. The one exception is that classes and levels are revealed in the player list that can be seen while selecting a character to play (immediately after joining a host). A fighter can still dress in peasant clothes or even a wizard's enchanted garments. The look of a character is not determined by his or her class but by the race, body type, and coloration chosen at character creation, and by the clothing and equipment acquired along the way. This will allow players to play any role they wish, such as a paranoid mage who hides within his clumsy armor or a petty rogue who puts on airs of royal birth.
Communication with other players will take on a number of forms. A robust chat system is available that will allow players to quickly and easily interact with others in their party. There is a also a quickchat system for sending preset messages. These are hotkey-activated, allowing for rapid and easy communication in most situations. Another benefit of the quick chat system is that it allows for cross-language communication, meaning that German and English players can still interact with their French counterparts at the simple press of a button. Real-time voice communication is not included in Neverwinter Nights.
The original concept for finding a multiplayer game was having the game present a list of running servers. When GameSpy stopped providing this list, several web sites took over the task of maintaining lists. While these sites cannot automatically find servers, they can check the online status of the ones they know about. With the coming of Neverwinter Nights Enhanced Edition, the game's list of servers has been restored.
The downside of a list of servers is that it shows just what is available, with little indication of whether or not one would get to play with others. The current player count provides a heuristic, but there is no guarantee. An event-based method for finding multiplayer games is provided by Neverwinter Connections, which facilitates connections between players looking to play together.