(How) You discovered a secret room! (Contest- Concluded)

How about a shovel weapon that drops from a certain enemy type. The shovel will do crap damage and is more of a joke weapon but even joke weapons can have their impact in-game. So you shovel a suspicious wall of dirt that leads to a hidden room. In that room lies a message. "Congratulations. You read this message for no apparent reason." <insert troll face here>.

How about a one eyed (or a no eyed) ghost familiar, that holds a candle light or lantern (there should be some willow o the wisps surrounding the light)... now this familiar should follow the player, when they reach a breakable wall, the willow o the wisps should float around the area, if the wall is not breakable the ghost should go to it and point at it.

I also think the familiar should reveal invisible enemies (it should take one time for each enemy... once an enemy is "revealed" the player should be able to see it anytime, though without the familiar it should be ghostly and see through).

Oh and one more thing, if there is such thing as leveling up familiars, the higher it's level the farther it can detect a hidden wall. 

I would be partial to a music-based puzzle that opens a locked room. For example, striking bells in the right sequence to play a tune (such as one of the Bloodstained melodies) or a word (classic use of this: original Scooby Doo and the "FEED" puzzle on the organ to open a passage).

I had an idea for a chimera boss battle,so I guess you could consider the secret boss room a secret room?
Anyways for the idea in a monster lab,you would have to gather a lions head, a goats head, a dragons head, and a serpents tail,all of which can be dropped from enemies within the dungeon area,now since alchemy is a thing in this game,miriam would do a little hocus pocus in a lab center aka a pentagram or transmutation circle,and the pieces would fall into place causing a monster to be born from some various magic explosions,the beast would fly off and a previously unaccessable area ...lets say a failed specimen dumping pit would become available,and from there you could battle the chimera as a boss battle which drops a powerful piece of armor and headgear

However after you kill the chimera's second form,it will speak in human language and warn that actions such as hers are the reason man is foolish since their curiosity at the creation of life and playing god to seek knowledge will be ultimately them creating a mistake a being that will one day cast a world in infinite darkness

So basically finding this secret room you earn:
-A boss battle
-An armor and headpiece
-A Dialogue from the monster once defeated that touches upon the ideals of the risks involved with alchemy and mans desire to seek forbidden knowledge

Aside from the musical idea, here's another one that sort of combines some of the other ideas:

Have 4 braziers on top of the castle (perhaps in towers, or some other locations; preferably exterior; any number will do). The player must ignite the braziers by casting different spells (or if weapons are elementally aligned, by attacking the brazier). Igniting all of them will then open a sealed door.

The braziers can be obvious (like on a pedestal as the only thing in the room; boss guarded or not), or can just be part of the background and not immediately obvious that they can be interacted with.

Further, the sealed chamber can be obvious (placards that illuminate when the corresponding brazier is lit; and perhaps even hints to the locations) or it can also be more subtly hidden into the background.

Presumably a door sealed in such an intricate way either holds a powerful object, a powerful monster, or both.

haha yeah, Plant 42. "Will you take the CHEMICAL?"

That real-world book reading could belong in the genre of alchemy/science at the time. There might be an actual recipe for an in-game item derived that way...it does sound pretty Igarashi-y (Igarashiee?) to me.

lai , to add on to that idea of "inconsequential item that ends up being important", I think that it'd be cool if such items were the results of failed crafting attempts. If there are varying success rates in the crafting system, I imagine one possible result could be some kind of a "junk" item that when used with something later-game allows something useful.

There have been some posts on things like this before, so it's hard to come up with something completely new...but one idea is that there could be something in the prequel mini-game that is very subtly hinted as being a secret, but it's not until later in the full game of Bloodstained that you can access it.

Say for example...there's a cutscene early in the prequel where Miriam, Johannes and Gebel are hanging out. A gift, badge, memento or some other kind of icon of membership to the alchemist's guild had just been given to Johannes/Gebel and they're explaining what it means to be inducted, etc, and offhand mention that the substance of the item itself has a chemical property to change its appearance when submerged in water. Later on in story scenes, in disgust or frustration with the guild (or one of the friends with another friend), Gebel (or Johannes) casts away this item unceremoniously towards a body of water that could vaguely resemble the castle moat. This area isn't explorable in that game, but can be accessed later once the player gets whatever the water traversal ability is in the main game.

Down there, the item from the story is just a rock. The only rock down there, so it kind of sticks out/doesn't fit in a way, but regardless appears to be like another bit of the scenery that can be hit, knocked around or carried (think a Yorick head). If the player realizes that this one rock could be what that one thing form the prequel changed into, after they go through the work of knocking it out of the pond, it reverts in the sunlight back to the original item.

Having this could itself grant entry into some kind of secret guild area, or used for equipping/crafting. You could even re-present it to Gebel or Johannes later to have them say/give you something else, or throw it back in the water lol.

Maybe in a certain area of the castle there'd be a strange little kind of monster that won't really try to attack Mirriam, and also can't be damaged by any attacks you try to use on it.

However, if you position Mirriam close to the monster, and use "Winestained", it will catch the glass, drink the wine, and scamper off to another room in the same area (of the castle). When you find creature again, do the exact same thing as before and it will happily dance around the room and trigger a switch that will open up a secret room.

TL;DR: Get a monster drunk, so it will reveal a secret room for you.

Let's say Bloodstained has a giant boss monster. After the battle, its corpse falls over and a door to a new area unlocks. If players share the same train of thought I do, chances are they'll just walk through that door. But if they either feel brave or feel like goofing off, the player can walk into the fallen boss' anus. The secret room is a boss's butthole. The player can collect some HP/MP increasing items, weapons, and armor the boss supposedly ate, but didn't poop out. None of it would be too dirty or gross though, video games don't have to be 100% realistic.