mystic eyes of death perception
A type of Mystic Eyes from Tsukihime and Melty Blood that are considered to be such a rarity that they are thought not to exist at all. Under the Noble Colors System, they are designated as Rainbow, the highest level, and are considered Divine Spirit class Mystic Eyes. The eye granted the user an ability to see the "Lines of Death" on a living being, and allowed them to "cut" it to instantly kill anyone.
They are possessed by Ryougi Shiki and Tohno Shiki. Also Michael Roa Valdamjong in the body of Tohno Shiki (2) displays a similar ability.