Background on inclusion of the riddle.
I have a player who is a riddle buff. She does them all the time and is playing a character that could reasonably solve them so it was kind of for her.
Additionally the PCs were all sitting there trying to think of synonyms for moderation and couldn't.
On top of that this is in a maze. The room had three entrances. Each one had a special lock but this was the only riddle. The didn't know it but they could have gotten into the room another way. The riddle was not the only alternative.