Porter served most of his life as a monk in the Order of Sigmar, tending to the monastery’s herb garden, and living a simple, cloistered life. Things changed for him when the visions started. He began to foresee terrible events, such as attacks by Chaos into particular villages, murders of prominent nobles, and natural disasters. The clergy tolerated this for a time, until two things happened. One, the scribe at the monestary began to transcribe and illuminate his prophecies. Two, his last prophecy involved the Emperor himself. The Inquisition quickly and quietly tried Porter the Grimm and the scribe (known only as Colemann), and ordered them put to death, and the copies of the prophecies burnt. Colemann was taken from his cell late at night, and hung. Porter was nowhere to be found.
Porter escaped to the foothills of the Grey Mountains, and lived out the rest of his life as a hermit. He traded with a small household of dwarves on occasion, trading his visions and dreams for food and company. Orcs eventually killed Porter in the night, but the dwarves carried word about the Prophet of the Hills into the Empire.
In recent times, the Last Prophecy of Porter the Grimm has turned up again. A printed version of his prophecies about the last days of the Emperor has made its way around Altdorf. The Church is not pleased, and is doing everything in its power to find the underground printing-press that is making these, and destroying every copy they can find.