In my fantasy project I have a vaguely medieval society (specifically the high period). However some of their religious practices are more along the lines of a iron age society. One of the biggest ones is they still practice animal sacrifice (I know some cultures did around the time, but I couldn't find many European ones, save things like bull fights)
In their religious beliefs Omnis, the flayed God, demands the use of sacrifices to appease for one's sins, but also to "balance" the world. Omnis flayed himself to make the world so in their theology everyone owes a debt to Omnis. This debt also manifests into "balancing" between the two worlds: the Waking and Dreaming world which becomes unbalanced with human actions ex: hunting. the payment of this debt is usually young and ample farm animals such as: goats, sheeps, cows. Usually a young healthy animal with the best sacrifices being virgin animals.
In the ritual the animals throat is slit in a very specific spot and the blood is drained out of the animal. The blood is not allowed to touch and thus defile the (usually temple) ground so it is collected in large jars. However after the sacrifice the blood can be used for whatever purpose.
What uses could a medieval society have for these large quantities of blood? I'm looking mainly for domestic and commercial uses since there is going to be a lot of excess blood.
Note: contact with blood is considered impure, but you'd just have to be ritually "cleaned" after using it. In universe people joke how butchers are holier then the priests since they have to purify themselves virtually every day.