A key unlocks a locked door between rooms. Keys are found on the floor they are used on, each one is colour-coded to the lock it opens, and each one works once.
How the colours work
A key opens the lock of its own colour. Matching is by colour alone rather than by a key belonging to one particular door, so what you are looking for when you hold a key is a lock of the same colour.
Colours are not unique within a floor. The same colour can appear several times on one floor — three of one colour has been seen in a single run — so a lock in a colour you have opened before is not necessarily a door you have already been through.
Using one
Keys are not consumed upon use; they open the door and remain in your inventory. However, they can be reused on other doors. If you attempt to use a key on the wrong door, you will take damage.
Put together with the colour rule above, that means a colour is not a single solved problem. If a floor holds three locks of one colour and you want all three open, you need three keys of that colour, not one key used three times.
Remember what keys you have used.
Finding them
The mini-map shows whether a room contains a key: as each room is revealed it is coloured by room type, and the display also indicates whether that room holds one.
Locked doors are not sealed doors
Two different things can stop you passing through a gate, and they are worth telling apart: * A colour-coded lock needs the matching key, which is spent opening it. * A seal is the vibrant purple field that covers every gate in a room while enemies are still alive. No key will open it; it lifts when the room is cleared.
That distinction is drawn by putting the first-hand notes above together with what the Rooms page already said about sealed gates. The two mechanics are described separately in each source; nothing here says how they interact on a door that is both locked and sealed.
Not to be confused with the Key Ring, which is a ring rather than an item.
First-hand: observed in game by the wiki's owner, October 2026. Unlike the community-sourced notes elsewhere on this wiki, this was seen in play rather than taken from a guide or a forum thread.