You aren't sure who's blood. You ask and they say, "it's the lord's blood". But Syb's blood isn't this dark. You know that for a fact. You've seen him bleed countless times. Most of them were nosebleeds, but one time you saw one of the cuts that he had. You hear something in your head ask, "what cuts". Well, let's do a little deducing.
Syb is a staunch opponent to suicide, so he probably didn't cut himself. How about his sister? From what you can tell, his sister is a bit abusive, you kind of got that vibe from her when you used to go to his house for sleepovers. Of course, those sleepovers, for the most part, took place in the large house because Syb hadn't built his own birdhouse yet. But yet, this solution has a hole, Syb's sister doesn't use weapons. You know for a fact, because she boasts about how she could punch a meteor in half if she had the chance. So, there must be some other option here. Let's take a few steps back, you only noticed his cuts when he was sleeping. At no other time did you discover them. So, this must be the solution. Syb was sleeping on Prospit and then got cut on his skin. Now, to think about who could've done the cutting. The Black Queen and her agents? Perhaps. But you doubt that the White Queen would let that happen, so it's less likely. Then who? Perhaps it's a question that will be solved far into the future.