Jon Jarl was a legendary Swedish jarl

Jarl in Sweden

In Sweden, members of medieval royal families, such as the House of Stenkil and House of Bjelbo, held the title of jarl before their accession to the throne. Since the early 12th century, there usually was only one holder of the title at a time, second only to the King of Sweden.For special...

 at the end of the 12th and in the early 13th centuries. He is mentioned in Eric's Chronicle from the 1320s to have spent years fighting against Russians

Russians

The Russian people are an East Slavic ethnic group native to Russia, speaking the Russian language and primarily living in Russia and neighboring countries....

 and Ingrians

Ingrians

The term Ingrians may refer to one of the following.*Inhabitants of Ingria in general.*Izhorians, Finnic indigenous people of Ingria.*Ingrian Finns, the descendants of Lutheran emigrants from present-day Finland in the 17th century....

 in the early Swedish-Novgorodian Wars

Swedish-Novgorodian Wars

Swedish–Novgorodian Wars were a series of conflicts in the 12th and 13th centuries between the Republic of Novgorod and medieval Sweden over control of the Gulf of Finland, an area vital to the Hanseatic League and part of the Varangian-Byzantine trade route...

. No historical evidence on the jarl exists, even though he may be the same "Johannes Dux" who lies buried in the Linköping Cathedral

Linköping Cathedral

The Linköping Cathedral is a church in the Swedish city of Linköping. The cathedral is the seat for the bishop in the Church of Sweden Diocese of Linköping. It is situated opposite Linköping Castle.-History:...

.

According to a 15th century historian Ericus Olai, he was murdered at his home in Asknäs in Ekerö

Ekerö

Ekerö is a locality and the seat of Ekerö Municipality in Stockholm County, Sweden, with 10,322 inhabitants in 2005.Agnetha Fältskog of ABBA fame lives on the island ....

 parish by the Lake Mälaren in 1206, allegedly by Russian pirates.