Blood is a resource often used around the world, as it would be very wasteful not to use it when slaughtering animals.
It can be used for cooking, and I can definitely see it being used to make curios or other occult themed buildings and items.
Should be harvestable by having a bucket equipped in one hand while slaughtering a domesticated animal, and each animal should yield 2-5l of blood(real world yield divided by 10. Can you believe a cow has a staggering 50l of blood in them?), depending on species, blood quality equal to animals quality.
Recipe suggestions:
Black sausage, made from blood, flour and onion, stuffed in a casing.
Black pudding, made from blood, fatty bits and wheat/barley seeds.
Palt, a dish made of blood, flour and raw meat, cooked in a frying pan.
Black pancakes, made from blood, flour, and honey. Syrup and/or onions?
Blood can replace eggs in some recipes.
This game is based in part of norse times, and so I propose being able to offer the blood of our animals to the gods in return for some favors or to get access to some dungeons. Quests?