DaggerXL was a rewrite of Daggerfall's game engine that was in development from June 2009 to April 2020. Designed by luciusDXL, the project was originally being developed alongside another engine rewrite for LucasArts' Dark Forces (called DarkXL), with the codesbases from both projects being merged to create the XL Engine in 2011.
The eventual goal of the project was to create an updated playing environment for Daggerfall, Dark Forces, Outlaws (by LucasArts), Blood (by 3D Realms & Monolith) and other classic games. The XL Engine was intended to allow these games to run on modern operating systems natively (as opposed to having to be run in DOS, or through DOSBox). Additional, Daggerfall-specific goals were to include the implementation of features that were initially promised for Daggerfall, but were absent (or only partially coded) in the final release of the game.
In June 2011, the DaggerXL portion of the XL Engine supported the rendering of any province and many different dungeons with high resolution graphics (including smoothed terrain and Bloom) and basic gameplay, including basic leveling. Quests and the plot had not been integrated yet. Additional gameplay features and bugfixes were being coded for future releases of DaggerXL, as well as ports to Linux and macOS. A map editor was also planned, which would allow for new exterior and interior cells to be included in DaggerXL as mods.
Beginning with its March 30th, 2014 release, The XL Engine project went through increasingly longer periods of time without updates. In December 2015, the XL engine was open sourced and made available to the public on GitHub, with plans for the first Beta to be released sometime in 2016. However, this never materialized.
On April 23rd, 2020, luciusDXL took down the XL Engine website and announced via a post on the project's GitHub that the project was officially dead, and would not resume development in the future, with their involvement ceasing back in 2016. They cited "other 'real life' commitments and a lack of time (and sometimes ability) to continue" as the motivating factors. They also commented that, in the years since, there had been other projects that had achieved everything they wanted to do with DaggerXL, and that people should look to those projects instead.
This article is based on the XL Engine section of the Daggerfall page on Wikipedia.
Daggerfall Unity — A project attempting to re-create Daggerfall in the Unity engine.