Starting in the 16th century, an island off the coast of Newfoundland was labeled as the “Isle of Demons.” Rumors spread that those who ventured near the island heard strange noises. Mariners believed that the Isle of Demons was inhabited by evil spirits; they were afraid to visit the island or to sail near it.
The cartographer Giacomo Gastaldi published a detailed map of the Isle of Demons in 1556. Featured below is a facsimile of Gastaldi’s map.

A facsimile of a map titled Nvova Francia published in 1556 by Giacomo Gastaldi. The facsimile was printed in Maids & Matrons of New France by Mary Sifton Pepper, 1908. General Collections.
The origin of the name Isle of Demons is uncertain. In 1424 the Venetian cartographer Giovanni Pizzigano placed an island named Satanazes on a portolan chart. Satanazes island was shown west of Portugal. The island may have been relocated and renamed on a world map that was published in 1508 by Johannes Ruysch. The Isle of Demons is shown as two islands on Ruysch’s map, as detailed on the right. Below is an image of the entire map, the red rectangle was added to show the location of the Isle of Demons near Newfoundland.

A facsimile published in 1893 of Vniversalior cogniti orbis tabvla ex recentibvs confecta observationibvs by Johannes Ruysch, 1508. Geography and Map Division.
The Isle of Demons was shown on maps near Newfoundland and Labrador from the early 16th century to the mid-17th century.
On the right is a detail of the Isle of Demons from a map that was published in 1622 by Jodocus Hondius and Jan Jansson.
An image of the entire map is featured below. The rectangle was added to mark the location of the island.
Andre Thevet, a 16th century cosmographer, priest, and explorer, wrote a book titled Cosmographie universelle. Thevet included a true story in the book about the French noblewoman Marguerite de La Rocque. Marguerite was the niece of the Lieutenant General of New France, Jean-Francois de La Roque de Roberval. In 1542 Marguerite de La Rocque accompanied her uncle on a voyage to a colony located in present-day Quebec. Marguerite began a romantic relationship with a sailor during the voyage. Jean-Francois de La Roque de Roberval disapproved of the relationship and left Marguerite, her handmaid Damienne, and the sailor stranded with some food and firearms on the Isle of Demons. Marguerite gave birth while marooned on the island. The sailor, Damienne, and child died on the Isle of Demons. Marguerite survived by hunting wild game; she was rescued by fishermen after spending two years on the island.
During the mid-17thcentury the Isle of Demons was removed from official cartographic records. Many theories exist about its present location. Some believe that Quirpon Island is the present-day location of the Isle of Demons. Another theory is that Marguerite de La Rocque, the sailor, and Damienne were left at Harrington Harbour, an island located in the Gulf of St. Lawrence. According to a local legend, Marguerite found shelter in a small rocky cave at Harrington Harbour. Today the cave is known as Marguerite’s Cave.
The locations of Quirpon Island and Harrington Harbour have been circled in blue on the map below.

Detail from Labrador and Adjoining Portion of Quebec by the Department of Justice Canada, 1922. Geography and Map Division.
There are many different versions of Marguerite’s story, and the Isle of Demons was shown on maps for a short period of time. In my opinion, we will never know the actual location of the island. The present-day location of the Isle of Demons could be Quirpon Island, Harrington Harbour, or another island near the east coast of Canada.