Discoveries

[Inco]

Crystals
as long as you don't eat the fruit your HP will remain intact and you will be able to collect crystals from various floor
some crystals are hidden under NPCs
there probably is an ending where you have to get every crystal or every locust without eating the fruit

Status Bar
From tree rooms you can enter the status bar and manipulate it like any other tiles in the game
you can remove yourself from existence, remove floor, remove tool or teleport to certain floors by switching locust counter with floor counter
apparently it is tied to one of the endings

Murals
Every mural has increasing number of marked tiles. It starts with 18 and increase by 1.
some murals are broken, but following above logic you can probably brute force the solution
you can enter murals as your emblem to get some messages

Picross
There is at least one picross puzzle
solution has the same layout as floor 25

Get judged/trial
if you're a perv then you get a trial scene
if you mess with your save file the game detects it and you get a trial scene
this scene puts you into B001 with all your locusts and rod and there's a brand new crystal there
new npc starts to spawn from now on, which will offer a shortcut
the shortcut leads to flesh floors

Chests
if you inspect the first locust chest multiple times, you get additional lore

[Inco]

Other items
there are other items than the rod
there are some square rooms with the same number of tiles as murals have

[Sanrai]

Further Judement
Force Quitting the game can save you lives, but do this enough times and you’ll be called to court for forcing your way through. Had this happen twice. At some point I started losing a locust every time I loaded the game and on going down a floor.

[Azebu]

Solving Murals
Sometimes you'll find a 6 by 6 room. If you rearrange tiles into a mural pattern (and hold the staircase), the background will change and you can drop down to a secret room containing variety of things. This allows for some sequence breaking too, as the room you end up with can send you many floors ahead (or backwards).

Items
On B023, simply pick up the staircase to enter Lord(?) Floor. Here you can find Void Memory, which lets you speak with rocks and decipher murals. Exit sends you to B025.
On B137, clear the room of enemies, then rearrange the pattern into mural found on floor (forgot, but it's the one with 22 tiles), to unlock Bone Floor, where you'll find Void Sword. It can be used to kill things directly in front of you.
On B157, rearrange the pattern into mural found on floor 57 (19 tiles), to unlock Fly Floor, where you'll find Void Wings. They allow you to fly over 1 tile gaps. Exiting the floor also sent me back to B71, possibly implying there's an earlier opportunity to get them.
On B53 the floor is almost all glass tiles, allowing you to solve different murals, but I believe you'll need wings for some of them, and there's also a single boulder preventing some patterns. Here I solved for Dragon Floor (16 tiles), The chest was empty for me, but the room contains another Picross puzzle. You can also move one tile here before dragon statues get pissed off, there is a gap but I can't fly over it and put staircase there without needing at least one tile extra. Exiting sent me to B181.

[Puru]

Ending:
When you have access to the status bar, you can enter the void by removing something tied to the floor (i think it's the letter B).
As you explore around, you will start hearing a sound that gets louder and louder if you keep going in the right direction, ultimately leading you to a strange cracked egg like structure. I'm not sure what triggers the ending but i kept hitting the egg by pressing forward and at some point the game asked me a yes/no option when i interacted with it instead of the usual dialogue, which led me to a secret ending.

[Azebu]

Potential Ending:
Once you get to the bottom, you are met with staircase in front of a statue that resets you to floor 1. However if you make the statue drop into void, and then use staircase, the game continues.

Special Brands:
Dying and then refusing the fruit "wipes" your progress, however meeting specific criteria will show you "Special Brand" that you can enter on your new run during engraving. Seems like there's ten slots for those brands.

[MyO]

Beginner, Learn The Magic Shape
To cross gaps, take the line -- one by one.

Stranger, Remind Yourself Of Futility
One level teaches you this: To try moving the immovable is to waste your time.

Quitter, Climb Farther to Live Longer
You can gain a lot of locusts if you've made enough progress. It's a simple matter of which one's which.

[Cap'n Crazy]

Originally posted by Puru:

Ending:
When you have access to the status bar, you can enter the void by removing something tied to the floor (i think it's the letter B).
As you explore around, you will start hearing a sound that gets louder and louder if you keep going in the right direction, ultimately leading you to a strange cracked egg like structure. I'm not sure what triggers the ending but i kept hitting the egg by pressing forward and at some point the game asked me a yes/no option when i interacted with it instead of the usual dialogue, which led me to a secret ending.

Been trying to replicate this, but I haven't had any luck triggering the prompt. Can anyone advise?

EDIT: Triggered the prompt. Dunno what caused it, but I spent nearly an hour and 8000+ steps bashing my head against it.

[Puru]

Status bar
If you have 0 locust and change the floor to B000, you will be transported to a room with a strange looking POI. Mine had two ropes burning when i visited which makes me believe there is more to it.

[Cap'n Crazy]

Chest manipulation
The contents of chests can be tripled by hitting the back of a closed chest three times, then waiting three seconds. There's a cue to indicate the tripling was successful.

Originally posted by Azebu:

Potential Ending:
Once you get to the bottom, you are met with staircase in front of a statue that resets you to floor 1. However if you make the statue drop into void, and then use staircase, the game continues.

Turns out this is (somehow) the normal game behavior and you can trigger this any time by setting the staircase in front of a statue on any given floor

[Inco]

Originally posted by Inco:

Murals
Every mural has increasing number of marked tiles. It starts with 18 and increase by 1.
some murals are broken, but following above logic you can probably brute force the solution
you can enter murals as your emblem to get some messages

there is no need brute force broken murals, simply interact with the left and with the right side of the mural

[Zylth]

B089 Secret Has a grid and a mapping of levels to locusts

The top code seem to spell "HERE WAS MNO"
https://steamcommunity.com/sharedfiles/filedetails/?id=3029907936

Cait Sith
On B117 if you knock the statue off the edge, a cat fairy shows up and gives you a kiss

[MyO]

On Hunger and Hospitality
Certain effigies have a craving for locusts. Why not share? You know how to make them fly out.

[MyO]

Originally posted by Inco:

there is no need brute force broken murals, simply interact with the left and with the right side of the mural

Strange, didn't work for brane 29.

[a]

Originally posted by Azebu:

Items
On B023, simply pick up the staircase to enter Lord(?) Floor. Here you can find Void Memory, which lets you speak with rocks and decipher murals. Exit sends you to B025.

I am on B023 and not seeing any option to do this? Picking up the floor does nothing

[MyO]

Originally posted by Inco:

Murals
<...>
you can enter murals as your emblem to get some messages

I believe those messages seem to be spoken by the Void Lords. One of them was definitely Lord Bee telling me to "get [my] own [brand"[/spoiler].