In the nintendo switch version examining the door leading to mad mew mew in the dog shrine before it is unlocked yields a message saying that the door is locked by a mysterious seal as an ominous piano jingle is heard.
Undertale the locked door in.
After that you go into sans room and will find another key on a box.
Save before talking to sans at the end then reload.
The door which bears the delta rune is surrounded by glowing mushrooms and floating particles.
There is no other way to enter this building.
Anyone that s started up undertale for the first time will encounter a mysterious locked door early in the game s snowdin area.
First you have to get the key to sans room.
Nothing will open it not even the expensive mystery key item.
Undertale by indie developer toby fox is a video game for pc ps4 vita and switch.
The mysterious door is an area found in snowdin forest south of the right side of the room with the icy x s and o s puzzle.
Come join the fun.
That key will open the back door.
Finally i got around to doing this.
It s not actually locked though and the bars are too wide to stop you from leaving.
To do that you have to save just before he judges you and then reload several times until he gives you the key.
Repeat a few times to get a key to his room.
Glyde can be encountered in this room before fighting papyrus.
Then snoop around there to find an another key that unlocks a hidden door behind the house.
If you are defeated by papyrus instead of seeing a game over screen papyrus will capture you and lock you in the guest room.
To open this door you must dodge every name during the special thanks portion of the credits after a pacifist run.
Don t worry though he gives you a nice bed and some food.