For the hidden missable trophy Backtracker in Immortals of Aveum, it's very simple. Still, it's an action you do all the time, and if you don't do it at a particular chapter at a particular moment, then even if you do it repeatedly, it won't count; keep that in mind. To get the Backtracker trophy, an easy way to know when to go for it is to check the chapter you are in. Its name is** THE MAGIC EATERS**, and the name of the objective is** REACH THE UNDERWELL**. It should be on the 9TH Main quest.  Once you have confirmation that you're in the right spot due to the image, all that's left to do is go to a portal and travel back to the PALATHON.  The trophy will pop after you travel to PALATHON.