While exploring through the game you will come across various collectibles; Gas Containers, Bone Saws, Guns, etc. You will need to collect a specific allotment of each one in order to obtain their corresponding achievements, as well as obtain all of them in order to get this achievement. Many of these collectibles can be found easily, through natural progression, while some are a little more obscure. Do not leave an area until you've discovered all collectibles, as some are missable. Follow the video guides in Rex, Baxter, Ronan, The Bell Killer, Julia and Cassandra's Story achievements, as well as the Codex, Eternal Flame, Salem's History, A Watery Grave The Bell Tower Banshee, The Heirloom, The Stalwart Specter, Man in the Box, Terror on the Tracks and Ashes to Ashes achievements in order to save yourself time and effort. As well, investigation clues do not count as collectibles.