The Natural Selection Annex or Creature Slaughter Dome is another Circle of Slaughter map. It is located to the right of the vending machines after entering the first structure in the Wildlife Exploitation Preserve with the collapsed telescope (eastern end of the map). It could originally only be accessed by purchasing a pre-order copy of Borderlands 2 from certain retailers that came with a special key for the DLC. It was released on December 12, 2012 as paid DLC and as a part of the Borderlands 2: GOTY Edition release on October 8, 2013. Entering without it is still possible if a pre-order or paid owner's game is joined. If the mission is obtained but not completed this way, access is granted independently until mission completion.