After the jewel is formed Kaname is able to siphon chakra from whatever in trapped within it, as a result of being sealed the being trapped within it does not die it is forever trapped within it. Kaname created this jutsu in order to seal away his father, due to him being unable to kill him by normal means. During an unknown time the jewel was embedded into his chest granting him an immense amount of chakra that his father possessed.