Statement: Age, meatbags. Its cutscenes were rendered by its own engine, and its people have fewer polygons than I have rivets. Its makers still sell the corpse, inside Jedi Knight on GOG and on Steam.
LucasArts' 1998 expansion pack for Jedi Knight: Dark Forces II. Kyle Katarn plays the first level, then Mara Jade takes over, and Kyle falls to the dark side in a Sith temple on Dromund Kaas until Mara duels him back. Fourteen single-player levels, with cutscenes rendered by the game's engine instead of live action.
General Tantor's remaster of Mysteries of the Sith on the OpenJKDF2 engine: upscaled textures, new models and in-game cutscenes in one installer.
Runs on
Windows
Needs
Your own copy of Star Wars Jedi Knight: Mysteries of the Sith (GOG's Jedi Knight: Dark Forces II includes it; Steam sells it too). OpenJKDF2 carries no game assets. To update the engine later, put a newer openjkdf2-64.exe (with its DLLs) in the Mysteries of the Sith folder.