Jibrael is a tall, slouching man with arms tied by what appears to be a bronze bugle. His first location is Petrous, which is accessed after the very first Prie Dieu in The Holy Line.
Before entering the cave where Jibrael presides, The Penitent One will give the Petrified Bell, the rite of access for the DLC. To go in, The Penitent One must be in True Torment mode by ascending the save file. Once inside, Jibrael will state how he is held captive by the Miracle as he is the anointed messenger of the Saeta. He tells The Penitent One that dawn will occur in time and so will the Amanecidas of the Miracle. Once leaving, Deogracias will stand in utter disbelief of how The Penitent One has awakened an ancient force.