How to Enter
Marni’s Secret Room can be entered by going to one of the following designated grind spots. Currently, you can only use Marni’s Secret Room at these locations.
You can view the list in-game, by going to the ESC menu > Adventure (F5) > Private Hunting Grounds.
Here you can view your remaining time, and each location will have a “locate” button which will show you a pathfinder to the grind spot.