The Dark Engine is the computer game engine used for the Looking Glass Studios games Thief: The Dark Project (1998), Thief II: The Metal Age (2000), and the Looking Glass/Irrational Games title System Shock 2 (1999).
The classic engine behind Thief: The Dark Project and Thief: The Metal Age. Features better lighting, sound propagation, and AI than any game before it.
NewDark has modernized the engine: Ttlg.com