"Fields of bodies, Mountains of dead
Down Dragonspring river, our country bled
A fiery god, demon wolf in red"
-Memory of Shura
Shura (修羅 Carnage) is what those who go on killing eventually become. They don't remember why, but they are simply enraptured and kill solely for the joy it brings them.
Shura is a Japanese way to call the Buddhism demigod of war Asura. It is also, in martial art terms, a path of carnage and destruction that awaits those who forsake their humanity in pursuit of power, immortality, fame, or fortune.