The Door key is obtained by searching under a flower pot left of the front door of the witch's house in Taverley. It is used to unlock the front door of the witch's house during the Witch's House and Grim Tales quests.
If the message "You didn't find anything interesting." appeared, then a player may need to start the quest first by talking to the Boy south of the house or the key may be in the player's bank.
This key cannot be placed upon the key ring.
In Grim Tales, a key may be obtained from Princess Miazrqa after Rupert has been freed (only during the quest).
There is a spawn of the key on the second floor of Nora T. Hagg's house.