The Developer Pack is a DLC pack that was billed as giving 'creative players some interesting tools with which to explore the Metro', prior to its release. The main feature includes a Shooting Gallery, a Metro Museum and an AI Arena, as well as a new singleplayer mission - Spider Lair - containing many Spiderbugs. The pack is included if you purchased the Season Pass, or otherwise costs $4.99/£3.99/€4.99. It was released on Steam and Xbox Live on the 17th of September, on PSN in North America on the same day, and on PSN for the rest of the world on the 18th September. The developer blog for this DLC is here.