What powers would a Seer of Blood have?

Guiding others to be more friendly and create bonds is a good start, although you can see how Kankri corrupted this into something not exactly good. Knowing what makes people get together in the first place and how to be friendly. Likely it’d let you know about circulation flow, so if someone has some blood disease chances are you’d know it. You’d also be able to See things relating to your Blood Caste, to your Family, and potentially even alternate versions of yourself- Like the Sufferer, who Knew about the Bonds people made in Beforus, Saw through the eyes of Kankri and dedicated his life to bringing peace to Alternia, Guiding others to be friendly with each other and not fight, trying to dismantle the unfairness of the Hemospectrum.