Deceased French Exile, Presumed Sorcerer
Details are sketchy, but there are a few facts known about Mr. Martensen:
Originally from the UK, Martensen spent his early years on whaling vessels in the South Pacific,. Charts he donated to Bouresches indicate he sailed around the (now) Gilbert Islands, with several charts reflecting charts subsequently used by Taylor & Taylor. He retired early, settling into a farm house directly outside of Bouresches around 1833. (NOTE: Edited from 1826 — not a major plot detail.)
At some point abroad he purchased interests in the St. Ives Transatlantic Company, the profits earning him a small but reasonable living.
Shortly after his arrival there are reports of attacks on animals and (less frequently) people. Corpses are found in remote locations west of Chateau-Thierry, with one of two points of commonality: either (to quote one source) “little to no signs of quarrel, bearing only the slightest amount of wounding about the face where the eyes were plucked out”, or to quote another account from a few years prior: “with the body rent apart, the insides termite-riddled and denuded of viscera.”
Eventually the people decide to equate the stranger with the events and in 1838 formed a posse to arrest (or perhaps lynch) John. He had fled the premises some time before, however, and so the town contented itself with taking items from the house. However, "Items deemed of no value, such as the jars of earth, were destroyed on site.”
One of the items seized is a small statuette made of wood. It has a very dark stain of a deep cherry/walnut. The wood itself is rather pliable, probably tropical, perhaps palm wood – in keeping with Martensen’s Pacific travels. The statue is very similar to the spiderlike statuette recovered from Dr. Godfrey’s room in New Mexico. Apart from an assessment of “over 100 years old” it exists without context.
Martensen resurfaces in 1840 in Big Bay, Michigan and has a house built over an entrance to a cave network. The house is also quite close to the Huron Mountain Dolmen. Disappearances start to happen once more, although this time spread out over two decades. Still, according to the journal of Stuart Cabot-Jenkins, the locals linked the disappearances to Martensen. He wasn’t able to escape a 2nd time and was lynched in 1884. Locals blamed his vengeful ghost for disappearances in 1887, 1888 and 1899.
You expect that Martensen was somewhere between the ages of 80 and 90 when he was killed.