As a setting it is most notable for being the world used for the persistent world of the same name in the role-playing video game Neverwinter Nights (NWN). Avlis as a persistent world spans 9 active servers and has one of the largest active player bases among such worlds.
The Setting 
Avlis is a traditional setting utilizing many familiar D&D concepts, such as crystal spheres, standard cosmology in the form of the Outer Planes, and several cameos of familiar gods and goddesses adapted to this setting.
However where many traditional fantasy settings rely upon the interplay of large cosmic forces of "good" and "evil", Avlis is focused more upon the concept of individuals and their alignment. Thus Avlis has no true "monster" races, rather each of the various races that populate the world are self-aware and evolving, with their own culture, language and nations that define them.
The Online Incarnation 
Started in late 2002, the online incarnation of Avlis was among the first of the Persistent Worlds built around the Neverwinter Nights game client. Many of the core elements that make up the backbone of running NWN persistent worlds were started with Avlis, including the crucial Neverwinter Nights eXtender (NWNx) and its various plugins such as Vaultster.
The online incarnation is very much an adaptation of Living Campaigns, but rather than limited to large scale events such as conventions, the persistent world concept allows for a similar degree of large scale adventures and participation on a regular basis. World history changes can be induced by player character actions and such are also reflected in the online incarnation of Avlis through area and system modifications.
Avlis is currently one of the founding member worlds of the Confederation of Planes and Planets, and has been featured in BioWare's Weekly Wednesday twice, in addition to interviews with various staff members (see External Links).
Print Incarnation 
An Avlis Campaign Setting Sourcebook titled "The World of Avlis"  has been released as a d20 book under the Pathfinder RPG license. Portions of the campaign setting were influenced by server events which occurred online.
Avlis contains many features expanding the Neverwinter Nights original content, such as:
- 17 custom races (9 base races, 8 sub-races), e.g. wemic, world-specific fey and elf subraces;
- The inclusion of religions to build into the role one may choose to play, also implemented in nine prestige classes for the holy warriors of each of the nine greater deities of Avlis;
- Enhancements and modifications to existing NWN classes allowing more role-playing styles, e.g. custom Barbarian rage effects based on either of the four elements air, water, earth and fire;
- Custom systems spanning all classes, e.g. advanced magic system with expanded spell list, animal companion training system;
- Custom systems related to general in game mechanics, e.g. persistent storage system implemented in player character owned houses and shops, player character death system taking into account the character's alignment to determine the destination death plane;
- Unique multilayered crafting system spanning ten crafts, many of which are interdependent;
- Its own custom background music and more.
The Avlis setting was fleshed out over time by two friends, Josh Simon and Ray Johnson, and played heavily by their D&D group from 1991 - 2002. With the release of Neverwinter Nights, Josh Simon moved the setting online with the aid of another close friend, Adam Colon. Avlis as a NWN persistent world begins with Josh Simon as a team leader, Adam Colon as a lead programmer, and Ingmar Stieger - creator of NWNx  - as a senior coder.
- Josh Simon, Ray Johnson, Adam Colon and Ingmar Stieger are known respectively under the nicknames Orleron, Ceardan, Silk and Papillon in the NWN-related internet forums.
Avlis was one of the first persistent worlds to open its doors to the public mere weeks after the release of Neverwinter Nights. The world has grown and expanded to include over 3000 areas to explore and immersive role-playing to experience, representing many walks of life. Over one hundred pages of history and details about this fictional world are available on-site.
World Forge Magazine 
The online incarnation of Avlis is partially funded by voluntary contributions from a portion of its players. This is largely achieved by players who subscribe to "World Forge: The Journal of Online Game Environments", an online journal which aims to give DMs and players a place to share their game settings and help each other develop them, as well as showcase fiction from amateur writers.
- http://nwvault.ign.com/View.php?view=gameworld.Detail&id=89 NWVault Profile of Avlis
- http://www.avlis.org Avlis website
- http://www.avlis.org/viewtopic.php?f=87&t=114531&start=0 "The World of Avlis", Campaign Sourcebook
- http://nwvault.ign.com/View.php?view=Interviews.Detail&id=338 NWVault Interview with Orleron
- http://www.nwnx.org/index.php?id=contact NWNx Contact
- Avlis website
- NWVault Profile of Avlis
- Neverwinter Connection entry on Avlis
- NWVault Interview with Orleron (Avlis 6th Anniversary)
- NWVault Interview with Orleron (Avlis Profile)
- NWVault Interview with Athena and Orleron (Joining Persistent Worlds)
- NWVault Interview with Papillon/Avlis team (APS/NWNx)
- Neverwinter Nights Extender (NWNx)
- NWVault Profile of NWNx
- NWVault Profile of Vaultster