NetHack Extended is a lesser known variant based on NetHack 3.1.3 by Juho Saarikko that was released in 1997. Its last known release was version 3.1.4. Over the years it has been lost to obscurity and its features are unknown because of lack of documentation with the release. As of today it is available to download from only one location on the Internet, on the website of MBnet, a Finnish BBS.

Download the variant here (You need to have an account at MBnet)