Here are a few possible interpretations for a Seer of Blood's powers:
Kankri style, whatever you take that to mean.
One who sees the connections between people. You are surrounded by people, and your place in their lives makes an impact. Similarly, your life is impacted by a endless web of people having an impact on other people. Take for example, the food on your plate. You might have gotten the food from the grocery store, who got it from a supplier, who got it from a manufactorer, who got it from a producer. In this instance, your life was impacted by AT LEAST four people, not counting all the people who work at the store, the people who handle the shipping, the people who invented the machinery to make it possible, or the countless other people involved in this process. The Seer would be able to see this web of connections, discerning the way one person is part of the greater whole of the community. This is the type of skill that can be unfathomably powerful in the right hands, yet is certainly difficult to master.
One who sees family and bloodlines. This is a lot more specific, and so has more niche applications. Great for all sorts of politics such as distinguishing royal birthrights, maintaining historical continuity, remembering everybody at the family picnic, and so much more! But not that much, reel it in now, no need to get so excited.
One who sees literal blood. This one might be veering too close to Mage of Blood territory, if there is such a thing. The power may take the form of a type of thermal vision, identifying anything in an area which may have blood circulation or blood that is not its own. Take it up a notch and see the still-beating hearts of everyone around you. Maybe this vision would also apply to other organic things like bones, cartilage, viscera, and other bodily goo. Now you can see real-time medical diagrams of people! Very useful, very creepy.
One who sees through literal blood. Now we're talking! Seeing visions reflected in pools of fresh blood, or scribing prophecies written in bloody ink? Making a bloody sacrifice of your enemies to gain forbidden knowledge and further your craft? Delve into the horror, and embrace the dark power that beats within us all! (Villainous applications optional.)
These are just a few ways a Seer of Blood's powers can take form.