Rivers of Blood is a Katana in Elden Ring. This is a cursed katana that has killed countless lives. Anyone who holds it will be devoured by an insatiable desire to kill, which will never be satisfied. Asier is the only one who can subdue and control it. And in fact, the sword seems to have chosen Asier in the first place as it guided Victor (who was possessed by bloodlust) towards where Asier was.