According to the Urban Dictionary a Blood Oath; is an agreement or contract that must be ordered and completed no matter what. In ancient times when people cut themselves or cut something like an animal, they would sprinkle the blood on the altar as part of religious action. They would swear to uphold and perform the task, no matter what.
Today a blood oath generally means that a person has sworn to do something, the individual must carry out their promise. The blood oath is usually being done by mobsters and crooks. In the story that I wrote the blood oath is made by the hero who tried to save the people that he loved, but failed and feels that the only way they can rest in peace is by making a blood oath so that in the next life they can rest easy.
