Mt.Moonspell Map Achievement in Vampire Survivors

Note: This achievement requires you to have purchased and installed the Legacy of the Moonspell DLC so that you can access the 'Mt. Moonspell' stage.

Load up that stage, preferably with Sigma, and all you need to do is follow the green arrow to find the map. This is pretty straightforward to find: head directly northeast like the arrow says, and you'll come to a building that it's inside. Head down and around the south side of the structure to find an entrance farther east. Head up, in, and immediately back west inside the structure to find a mini building within that has the map you can collect. Feel free to quit out immediately after grabbing the map to unlock this achievement.