Porphyricus is a Death Guard Sorcerer, who once held the rank of Librarian, in his Legion during the Great Crusade, before he joined his brothers in renouncing the Emperor and dedicated himself to the Chaos God Nurgle during the Horus Heresy. Despite this, after nearly 10,000 years in the service of Grandfather Nurgle, Porphyricus has barely received any favour from his patron. Frustrated and dismayed by this lack of recognition, Porphyricus has resorted to ever-more depraved ways to draw the attention of the Great Corruptor. Among the atrocities he has committed, was the creation of a sorcerous plague that infected just one person at a time on the Imperium world of Castix VIII. When the Guardsman who was first infected died, the company medics thought the plague was gone, only to find someone else had been infected the next day. These peaks and troughs of hope and despair were Porphyricus's gift to Nurgle, but they went unnoticed. He then ruined an Agri World, during the Goanic Crisis, with just a single sorcerous conjuration. This also failed to gain him notice, so in the Battle of Withering Breach he reduced an entire Ork horde to mutated fungal spores. His actions left the world the Orks were on to rot, but he was still not rewarded. However, unknown to Porphyricus, Grandfather Nurgle knows of the Sorcerer's efforts and enjoys his servant's despair.
Once Porphyricus traveled to backwater planet of Azbaragus where he founded the diseased population slowly dying because of some unknown illness. Clever Porphyricus immediately offered to the inhabitants the salvation in a form of the worship to Great Corruptor. Desperate people agreed and soon the planet became in Nurgle's possession. Since that time The Blighted - Cultists of the Nurgle - joined the Porpyricus' Death Guard army, serving as faithful retainers to their new masters. Their leader - Noxious Clave, pox-ridden demagogue, leads them to a new plagued future.