Cap 1144: Alliance part 1
Of all the people here at this gathering, my sister in her current state was far from the strongest, but someone as old as her who is known as a Living Catastrophe has already caused so much death, I can't even imagine the number of lives taken by her hands, killing intent is a separate aspect of one's Aura, a mark that shows the number of lives taken.
I only realized this because I didn't have anything like a killing intent when I was born in this world, I also only noticed that I had something like this after the Goblin Village massacre, since then my killing intent grows more and more to the point of being stronger than my normal Aura.