Ok, first of all, these are just a few theories I have, some people may have already thought of them, but I'm going to post them anyways.
Clockwork Lullaby/ Wordplay[]
My theory about this song is that the songs are sung from the perspective of the singer, being the same person in both songs, not much is known about these two songs and hbaow they tie in to the Chronicles, but I believe that when the series is completed the facts about these two songs will be revealed.
I believe that the songs have something to do with the sin of Pride because of some of the lyrics in Clockwork Lullaby, speaking about human desires in a haughty manner, therefore urging me to think that the singer is something related to the sin of Vanity.
Venom Sword and Kayo's Scissors[]
In"Ru RI Ra, The Resounding Song" there is a line stating that " A blade was wrongly dipped in the spring" the spring was the original form of Envy, and the blade mentioned could be the Venom Sword, thus creating my half-baked theory on why Kayo's Scissors and the Venom Sword will not awaken. It's just a theory, so it could be way off.