Purchase the Prototype DLC and receive the following extras (available for PC, Mac and linux) for The Talos Principle:

• Prototype Levels - Includes more than 100 puzzles from early prototype development stage and 1 exclusive level from early beta version, not present in the final game.
  
• Elohim Voice - US version - Elohim voice narrated by Serious Sam narrator Bill Jurney.
  
• Elohim Voice - Writer's prototype - Elohim voice narrated by The Talos Principle's writer Jonas Kyratzes.