Mark of the Shitōshin

The is obtained if one of them scratches ones back. It causes one immense pain when glowing. When the mark is glowing, it means fifty years have passed, and it is time for a new sacrifice. If one possesses the mark, and goes to Hōrai Island, they will be unable to leave. Each mark represents one of the four gods, and each time a god is destroyed, a mark disappears: the first when Sesshōmaru defeated Kyōra, the second when Sango slashed Jūra, the third when Inuyasha slashed Gōra, and the fourth when Inuyasha destroyed Ryūra fused with the souls of the other gods. When all four marks have vanished, and all four gods are dead, the person who once bore the mark is now free to go.

Krallensiegel der Shitōshin