Celia Baskerville
Celia was a Baskerville, 100 years prior to present day. She legally contracted with Humpty Dumpty sometime after Glen transferred his soul from the body that once was Humpty Dumpty. Her close connection to Glen is why Humpty Dumpty chose her, as it was Humpty Dumpty's job to protect the soul that was once in its own body, which was now in the latest Glen Baskerville. She once showed Jack her Chain and its ability to create many duplicates of itself, thus, he found Humpty Dumpty amazing. Some how Elliot Nightray ended up with her Humpty Dumpty, apparently making Elliot have her role from 100 years before, to protect. Humpty Dumpty claims that Leo needs to be protected and attacks whenever either of them are in danger. It is assumed that Celia and her chain were dragged into the Abyss and their contract nullified, which is why Elliot was able to contract with it. Source: Pandora Hearts Wiki