Where to use Jack, Queen and King keys?

[Discy]

This.

[Re4XN]

One Jack key is required to access a room in the Thieves' Tower.

[Miniwizard]

One King key is also usable in the castle cellar (where you went for the early quest to get the diary)

[AEon]

The Queen "Q" key can be used in the game's starting area, Prison, on Hammer Island, blocks off an exit. Opens a new map called the Prison Annex Below..

Trouble is I knew of all those keys but have not found a single one? Do I need to kill Blight first?

[AEon]

After a few things have been fixed in Fallowfields and the main town, you probably need to talk Luke in town prior to all this. He will then fix the broken bridge north of the Maze, returning to his home there. Only in his house there will sell you several gold, silver and bronze keys, and offer some unusual ones too: King Key, Queen Key, Jack Key.

Strangely, he will sell up to three keys of each... why would you need more than one of each? Hmmm...

[SuperContact]

I didn't find any other exits on the Prison area that can use keys on