Mutantstein III: Nightmare's End is the twenty-first mod released by John Bucksnort. It was released on April 9, 2001 - roughly one year after his very first mod, Grossed Out.
It features 6 levels, played in a custom EXE based on registered Wolfenstein.
This would be Bucksnort's final entry in the Mutantstein series. His grandson Bobby would continue the series after John passed away, releasing Mutantstein IV: Darkworld in November 2001.
An SDL port was released on September 30, 2012.