What do cursed keys do?

After entering a lock a door that you unlocked, the door is automatically locked and you can no longer unlock it.

They unlock anything, until you come to a lock you really want to unlcok. Then they break in the lock. The pieces of the key fuse themselves to the lock, so that it will be forever locked.

...

Opens any door to the worst possible place

Open cursed chess with cursed demons inside.

Jingle all day and all night with no way to muffle the sound.

youtube.com/watch?v=HU-MGQksnZ4

Automatically bind to your person upon touching them, disappearing. Whenever you use a key, there is a chance (seemingly dependent upon how much trouble it would cause for the victim) it will replace the key you are using as it is being turned.

After that, there is an assortment of random effects it could have, including:
-Disengaging all locks in a 10 mile radius, and rendering them permanently inoperable
-Makes a very loud noise, sticks in the lock, and sticks to your hand
-Teleports you to the other side of a random door on the planet

Acts like a skeleton key unless you're at risk of dying if it fails to work.

Acts like a skeleton key, but with a very high chance of actually summoning a hostile skeleton on the other side of whatever you are unlocking.

any door unlocked by them will take you some place you really dont want to be

It acts like a skeleton key, but can also unlock the potential of one who possesses it, giving them effortless expertise in many, if not most things.

Unfortunately, sentient species live in a conscious space just beneath the attention of... "Other," stranger consciousnesses. The unlocking of all potential without the protections of practice to build immunity can cause someone to be thrust unprepared into Their realm of consciousness, and subsequently attract their attentions.

Not if you like your kidneys

They open bitch's minds.

The skeleton the key was cut from ?

I actually really like this. Maybe not necessarily a skeleton, but whatever monsters were in the room are all staring at the door as you enter or something. You can always get through a door, but you always walk into the room on the other side at the worst possible time.

Both the blessing and the curse are negated, leaving you with a mundane but otherwise functional lock and key.

>insert Key of Doom in your closet door
>turn
>get this

Start a lackluster videogame series using a paradoxical mix of western kiddie cartoon characters and edgy teenage eastern characters.

Turns the unlocked object into a mimic.

I feel as though I saw this in a cartoon at some point

Simultaneously relocks anything it unlocks, rendering any further attempts to open the lock futile and only by locking again with the cursed key can the cursed relock be unlocked to allow any other key to work on the lock. Ultimately it was to be a magical security device, to require two keys for one hole.
The problem being that the cursed key may or may not disappear into thin air after it's being used.

It opens anything but to use it you have to stare at what you want to unlock and then stick the key up ya butt and turn until the real lick opens.

Keys of Breach I'll call em!

Instead of closing doors they open it and instead of open doors they close it.

When unlocking the door, the hinges swap sides, making for a slight inconvenience openning it.

They open the lock, and the door leads into the nearest Mordenkainen's Magnificent Mansion.

No wizard likes an uninvited guest, man.

The key is symmetrical but you always have to take it out and put it back in the other way around.

Lo and behold! The 18 cursed keys. Built by a dark hand long ago. Whosoever finds one of these keys, do not use them! For any lock opened by one of these, shall unleash a nightmare into this world. - Words inscribed upon each cursed key.

The keys were used to lock away 18 unholy monsters long ago, and by doing so, the monsters cursed the keys. Now, if the keys are used in any lock, it will release that corresponding monster back into the world, to wreak nightmarish devastation once again.

> The key fits any lock, but refuses to turn it. Used to delay thieves.
> The key fits any lock, but when turned inside, it seals the lock in its current state, either opened or closed (possibly by filling in the lock with liquid metal)
> When inserted into a door, the key randomly creates a portal to another doorway in the vicinity (the door obfuscates this effect until the portal is passed through)
> When used to open a door, the doorway becomes a portal to a random fiendish plane, effectively acting as a greater gate and alerting all demons in the nearby area of the breach
> Key produces a strong electric shock when put in a lock
> Key produces immense heat when put in a lock
> Key produces loud sound when put in a lock
> Key is sapient. Declares it can open any door, but asks for favor first.
> Key is actually a small sword, wielded by a mouse knight who will hunt you to the ends of the earth to have it back
> Key will randomly disappear and reappear at will. If put on a keychain, any key becomes subject to this effect
> Key always finds a way to stab you in the thigh from your pocket
> Key will open any door in exchange for blood
> Key is invisible
> Key sends a silent message to the owner of whatever door it is opening alerting them of the entry
> All locks fit with the key explode

Any time you fall or tumble, you invariably land on your keys, grinding them into your genitals.
Even if you put them in your backpack.

It opens any and all of YOUR locks, and you keep dropping it, forgetting it in the locks, and so on.

I was hoping for an explosion :(

Cursed keys are dangerous in part because they are subtle. For example, some cursed keys open and close doors in exactly the same way a normal key would, but curse anyone who passes through a doorway opened in this manner.

...I also really like the idea of a cursed key that can turn any lock exactly twice, and no more.

According to the chart they can't breed with out intervention of a deity.