Belgian sorcerer and writer (???-1542). His name is sometimes recorded as Ludwig Prinn, though he appeared to prefer spelling his name with the "v".
No one has any idea when Prinn was born. He claimed to be hundreds of years old. He also said that he was the only survivor of the Ninth Crusade -- and in fact, there were old records of a Ludvig Prinn who fought in the Crusades, though the obvious explanation is that one of Prinn's ancestors was involved in the conflict. 'Cause you know, it's impossible for someone to live hundreds and hundreds of years. Right?
It is, however, quite well-established that Prinn did more than his fair share of traveling. At various times, he made trips to Rome, Alexandria, Cairo, Jerusalem, and Baghdad. He was captured and held prisoner in Syria's Jebel Ansariye, where he ended up studying ancient texts with local scholars and mystics. He also claimed to have visited with the notorious priests of Nephren-Ka, the sinister but (hopefully) mostly-legendary Black Pharaoh. He spent some time in the ruins of Chorazin on the Lake of Galilee and in many-columned Irem -- neither of which sound like picnics, considering some of the gruesome legends there are about those cities.
After a decade or two of travel, Prinn took up residence in the Flemish countryside, living first in Bruges, then Ghent, and finally in a pre-Roman tomb in a forest near Brussels. Rumors quickly started flying that Prinn was consorting with demons, conjuring invisible familiars, and bringing forth monsters to eat the local children. It didn't take long for the Roman Inquisition to come calling, and Prinn was imprisoned on charges of sorcery.
While imprisoned, Prinn began writing his masterwork: De Vermis Mysteriis, or Mysteries of the Worm. After a few months of work, Prinn finished the book and somehow smuggled it past his guards one night. It was generally believed that he bribed one of his jailers, though Prinn suggested that he had help from... other sources. Unfortunately, his other sources couldn't stop him from being executed not long after the book was published.
Much of Prinn's original manuscript was written in what appeared to be Celtic runes, though this may have been a simple code. About a year after his death, a Latin edition of De Vermis was published in Cologne. It included a wealth of occult information: necromancy, divination, and conjuration took up large chunks of the text, along with several pages on vampires, a tentacled, crab-clawed, toad-like monster called Byatis, and the "worm-wizards" that Prinn claimed he studied with in Irem. Prinn also includes a lengthy and nightmarish treatise on the Egyptian crocodile god Sebek which suggests that he actually communed with and narrowly escaped from the god and his legions of reptilian followers. However, the most famous chapter of De Vermis is "Saracenic Rituals", which includes, among other things, spells for calling down invisible demons from the heavens, incantations to allow one to "see between spaces", the recipe for a hallucinogenic/time-travel drug called Liao, a description of the land of Yoth, an underground nation populated by snake people, and numerous praise-and-worship rituals for entities a good deal older, more powerful, and more horrific than the Yahweh of the Old Testament. Only three copies of the book are known to exist: one in the Huntington Library in San Marino, California, one in the Miskatonic University library in Arkham, Massachusetts, and a fragmentary copy in the British Museum.
A little known postscript to Prinn's life: the judge, prosecutor, and defense lawyer in Prinn's case all died less than six months after Prinn was executed. The deaths of the judge and defense attorney were written off as wolf attacks, though they were nowhere near any areas where previous or subsequent animal attacks had been reported. The prosecutor's body was found in a deserted field; witnesses said it appeared that he had been exposed to freezing temperatures (this was in the hottest part of the summer) and that it also looked like he had been dropped from a great height. In all three cases, church authorities ordered the men's bodies burned after examination. No explanation was given, and the case records have been locked in the Vatican's so-called D-stacks for the past 460 years.
Encyclopedia Cthulhiana by Daniel Harms, p. 50-51, 171-172
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"Lord of the Worms" by Brian Lumley