The Mistborn Saga: The Original Trilogy is a 5-book series with 3 released primary works first released in 2006 with contributions by Brandon Sanderson.
The Original Mistborn Trilogy, AKA Mistborn Era 1, consists of 3 main books, a prequel short story, and a novella at the end. Follow the story of Vin, Kelsier, and their crew in the Final Empire.