So, I managed to get pretty far in the sidequest involving the chess/royalty keys. I picked up all of them I could find (Peasant key, Knave Key, etc etc), didn't break off any in the lock by the table in Block 7, and eventually found a door that one of them (I think the Knight key?) opened in Block 8 or 9. Behind this door was a spooky demon.

I answered its riddle correctly, and it gave me a black candle. Using this on the table in Block 7, it finally gave me a key I could use to open the locked door on the level. (I think it was the Queen key) So I opened that door, took the Bishop key from the chest, used it in the correct door in the same room and got the Rook key.

Finally, I was able to use the Rook key in a door on the Upper Levels, and this led to a room with three more doors and another demon. This demon didn't want to play riddles, it just started a fight. It gave me the King key when I killed it. And then, at long last... the King key didn't appear as an option for any of the three doors. And all other keys I'd collected that WERE options just broke in the lock (I think the options it gave me included the Emperor key and a couple others).

I combed the entire game looking for something I missed, but there was nothing. No more keys. Plus the door to the final room wouldn't open again when I came back, and I couldn't get another Rook key to open it because the door leading to the Bishop and Rook keys ALSO wouldn't open without the Queen key, and the riddle demon wouldn't give me another black candle to get a new Queen key.

So, at this point I just gave up and finished the game. Does anyone have any idea if there was actually a way to complete this quest, and what the reward would have been? I explored the dungeon extremely thoroughly and I believe the only thing I missed was one of the stones for an altar on one of the earlier Blocks, because the box I think it was supposed to be in was already opened when I found it. Did the altar give a key I needed for the chess quest or something?

Unfortunately it's been bugged since release. The dev attempted several times to fix it but it never worked, and the last update was in May. Try checking the Steam forums to see if there's any new, he used to be in contact and replying to the bug reports thread there, however he hasn't actively replied since June or July, so I'm not sure if there will be another patch or he's just busy with other projects. He did post that last update after a long time though, so we might still have a chance, there always was something like not getting the right key, then something else broke etc.

Or he could just try to hire someone to look into it for him.

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