The wiki says, Apparently, this room can be found without the compass, by combing the maps.

However, I lucked out and got three shrines in a single map, two of which provided compasses, which led me to two secret rooms in the forest and in the darkness.
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Do these rooms actually exist without the compass? Are they accessible? Alternatively, are they generated when a shrine with a compass is placed on the map? when the player finds the compass?

How many rooms are there? One per map + additional rooms when required? One per zone? No rhyme or reason?

Is there a reliable way to search the map for the secret rooms? Is there a pattern for the positions of the entrances - can they be in the air? above solid furniture? in the permanent spikes?

Thank you. I was primarily interested whether combing the castle for a secret room and a possibility to grab a game-changing item when I suck at the game (or just started a legacy) is a worthwhile investment of time. Apparently, it isn't.

I personally think it´s just easier to play normally than trying to lock the castle or get lucky with some room. I lost much time on my first playthrough trying too hard to get everything in every room by locking the castle. The game is actually a lot easier without locking the castle and just getting as much things as you can each time. Don´t stress yourself if you miss something, I think there´s nothing so good you won´t be able to find in a couple of playthroughs.

I usually just keep myself on one area, cleaning the rooms unless they are too hard or I´m at too low health. Sometimes I sneak a little into other areas, but I fastly go back if there are enemies closer but no treasure at sight. It doesn´t matter if you die, as long as you can get something new after each time (yeah, sometimes you die before that, but who cares if you improve on the next one).

Secret rooms aren´t that awesome once you get the game going. They are a nice boost, but I think searching just for them will end up wasting more time than they are worth. I may be wrong though... I´ve played the game once until NG+8 but I´m not a pro at this game and I don´t know how everything works, so this is just my opinion.