Black Judge:
At the other end of this chain is the Sin Eater. He is your brother, and will come if you call his name. Now you must leave. When you have completed your penance once, come back and see us. That will be the time when you two will part your ways. At that time, you will be released from the manacles.
(When the Sin Eater advances one level you will have completed this quest.)
All of the Exp that the character who summoned the Sin Eater has acquired will be transferred to the Sin Eater.
When the Sin Eater becomes hungry, you can feed him "Food For Wolves."