We have a witness, but they have no memories and could actually be the murderer.
Sol is a big, beautiful teddy bear. It's hard to believe he's capable of murdering witches. And Azren doesn't know what his motive could be any better than he does. It doesn't make sense, but there's no one else it could be unless they are just really good at hiding.
We can get all of Sol's memories back and hopefully exonerate him. We just have to locate a very tricky raven who likes to speak in riddles. No problem, right?