In the Ritual Edit
Once passing the Gate of Boundaries, the Knight will meet with the current Black Guardian. The Guardian will then gather all of their remaining lifeforce and pass it onto the Fafnir Knight, thus passing on the title of Black Guardian onto the Fafnir Knight. This is done to renew the Seal of the Yggdrasil Core, thus completing the ritual. After this, the former Black Guardian's spirit die and pass on. From then on, the new Guardian will remain in the temple for the next hundred years until his lifeforce is drained. Only then will the next Fafnir Knight appear and come to renew the lifeforce.