Crawl

For this achievement, you must discover all monsters, weapons, items, and objects in the game.

Monsters - You must play as the monster for it to be added to the vault.
Weapons - You must purchase the weapon from the shop.
Item - You must purchase the item from the shop.
Objects - You must interact with it/activate it.

I created a video showing all of the Vault. I go through them quickly, but just watch it in slow motion or pause if you want to get a good look at a specific thing you are missing.

Special Note: Object #4 is currently bugged as of 4/21/2017. According to the dev, only 30 percent of these will unlock the vault entry. I had to interact with six or seven of these before it appeared in my vault. This has already been patching on pc, so I would assume a console patch will come later.

Update: Object #4 was supposedly patched and should unlock correctly. Anyone able to confirm?