Master Explorer is arguably one of the most frustrating trophies in ScourgeBringer. Clearing every room sounds pretty easy on paper, simply look in every possibly area, though secret rooms can be rather challenging. On later levels they can be difficult to find and needing bullets means there are a finite number of guesses. Thankfully, there are some details that make this task a little more manageable.
Since Master Explorer requires a successful run of ScourgeBringer, I strongly suggest maxing out health, obtaining fury and ideally having every skill. In addition to that, any run where any rapid fire and/or high ammo weapon is obtained early, makes this significantly easier. Without knowing the actual location of some of the rooms, it comes down to guessing, so the more area you can cover the better.
In a standard five realm adventure in ScourgeBringer, there are a total of 100 possible rooms. Each realm also following a distinct and important map arrangement. Every realm has a total of three item rooms that will either be broken up into two shops and a hidden room or one shop and two hidden rooms. If you’re ever in doubt, check the map, count the shops and hidden rooms and never leave with less than three. Finally, if you’re in the position where you still need it and lack ammo, buying a new gun will give you ammo.
Getting Master Explorer is, almost in a sense, luck based. In the event you haven’t unlocked Treasure Hunter, hidden rooms are optional areas, with some kind of item, that requires players to break the wall. The simplest way to do this is to shoot, though tossing an enemy or fury can also reveal it. On the first floor it will have some sparkles that can easily be seen, a trait many users claim continues in a less obvious way, though I couldn’t find a consistent look or answer in my journey. That said, it really isn’t too hard to guess either.
The general rule of thumb is pretty simple. A secret room can only appear on an open side. So, if you see a gate, that side can be ignored. They often appear in locations or positions that stand out. Places with too narrow an opening won’t have a secret, nor will traps or anything fixed. Just keeping these elements in mind can vastly decrease the amount of potential paths.
From there, shoot literally anything suspicious if you have ammo. Getting ammo isn’t terribly difficult, though getting it without enemies can ruin a run. Finally, make sure to check every possible side. It was surprisingly common for one side to have it in an outlandish position, with a different area putting it in a rather obvious spot.