Interesting... while looking for these Riddles, I found a "new" section in my COMPLETED quest log
- "Moria Hidden Content" -- one of the quests there is labeled:
- Hiding content - DNT - Quest:Riddles in the Locks.
Which is part of the Riddles in the Dark Quest Chain.
-  Riddles in the Library
Completing the above quests then unlocks:  Riddles in the Sunshine .