The Intercessor, also known as the wandering Bard is an Immortal entity of possibly human origin. Her original name is unknown and it is not clear if Intercessor or wandering Bard are Names. She seems to work for the Gods Above but her current goals are unknown. She is known to die and return in another body under a different name. She was first known as Almorava of Smyrna but died after the callowan rebellion failed. Her next form was known as Aoede of Nicae. At the end of the Epilogue of Book IV, she appeared in front of Amadeus in a new form, claiming she was now called Marguerite of Baillons.
She seems impervious to attacks but has to flee them at some point, most likely after the third attack on her, as she fled from Amadeus at that point. When she flees she enters Nowhere and may need to stay there for some time.
Neshamah was able to physically hurt her and dissected her body. He found her body completely normal but speculated it to be a perfect construct.