Ori and the Blind Forest

Secrets in Ori and the Blind Forest are areas of the map that cannot be seen initially but are revealed when you walk into them. You can also unlock the ability to see secrets once you max out the Utility tree.

There are a total of 43 secrets in the game, once you enter any secret for the first time this achievement unlocks. I completed this right after the Prologue as the first accessible secret is right at the start of the main game.

Here is the link to the solution by LifeExpectancy who included a video showing the locations of all 43 secrets.