Fraternity of Shadows
Fraternity of Shadows can refer to any one or more of three things relating to the Dungeons & Dragons setting of Ravenloft; an in-setting group, a website, or a particularly dedicated group of Ravenloft fans.
In the Demiplane of Dread, the Fraternity of Shadows are a secret society of wizards and sorcerers, predominantly illusionists, who have stumbled onto the truth about their world being artificial and who have dedicated themselves to unraveling its secrets so they can usurp control of the world from the Dark Powers and become gods.
Once, there was a bunch of Ravenloft fans called the Kargatane, who used the primitive internet of the 1990s to organize fan discussions and generate fan content, creating the first of the Ravenloft netbooks. That group eventually disbanded, with a number of them actually being recruited by White Wolf as authors for their Dungeons & Dragons 3rd Edition licensed update of Ravenloft. The Fraternity of Shadows fan-group rose up to fill their shoes, creating a single dedicated website with forums, archives and all sorts of stuff to keep the fanbase alive and thriving, even as official support for the setting from Wizards of the Coast slowly dried up over the years.
The Fraternity website, linked below, is THE gathering place and hub for Ravenloft fans on the internet, having been going strong from the early 2000s til today. Fans get together to discuss lore, talk about experiences, play online games, debate ideas about tweaking or changing the setting, and generally have fun. Although not as bustling as it was in its heyday, when Ravenloft 3rd edition was alive and well, it's still chugging resolutely along, hoping against hope that Wizards of the Coast will finally do something to bring back the full setting and working on their own updates of it to Pathfinder and Dungeons & Dragons 5th Edition in the meantime.
Amongst its many qualities includes serving as a respository for all known Ravenloft netbooks, including those created by the Kargatane as well as Van Richten's Guide to the Mists and their own yearly Quoth the Raven publication.