Jon Jarl was the man who discovered Jorvik. He came to Jorvik in October 1218 with his crew and settlers. Jon ruled Jorvik and its small kingdoms for 45 years. One of the clans on Jorvik known as the Silfer Clan was made up of his descendants, and the descendants of the clan members still live in Jorvik. He is buried at Jarl's Tomb near Fort Pinta.
"I am Jon Jarl, son of Jor! This land is now my land and I name it Jorvik and I shall defend it with my life as long as I live and with my soul after I am dead!" -The Jarl's Oath, taken after discovering Jorvik
It was October of the year 1218 when the Jarl and his ships approached Jorvik. The people were running out of both food and hope, yet didn't dare to object to Jon, whose resolve and faith in the visions given to him by God was the only thing holding the expedition together. In the direst moments of their pilgrimage when even Jon's first mate, a man undyingly loyal to his Jarl wanted to end his misery, they finally saw land on the horizon. It was the land Jon's God has shown him and it would become the land of his descendants. For a more detailed description see Look for clues in history - Book 1.
As Jarl's people explored the new island of Jorvik, they found rune stones created by people with a special connection to the island's magic - and Jon ordered all of them to be destroyed to prove his claim to the island. The people tried to destroy them, but some perished doing so. Jon then ordered the fabled Magnus Steinar to split a rune stone close to his stable in two, which resulted with the Jarl's horses being driven mad.
Jon decided to make peace with the island's druids and in return he was rewarded with many strong horses. The Jarl might have also forsaken his old ways in the process, choosing to follow Aideen rather than his God, which greatly angered some of his people. Seeing Jon as a traitor, they chose their own Jarl and led an assault on Jarlaheim. The Great Jarl won - but his victory was bought with the blood of many of his loyal subjects.
The only man standing after the assault was the man who would become Galloper Thompson - and when the Jarl found out that the man gained immortality, he envied him and ordered him to bring Jon the secret of immortality. It's unknown if the man wanted to give his liege the secret and his efforts were sabotaged or if he wanted to keep the secret for himself, but the man greatly angered Jon shortly after and so he was to be executed.
When the executioner's axe came down, however, the headless man stood up and after escaping he became the Jarl's sworn enemy. The Galloper patrolled the King's Road, attacking anyone he deemed as loyal to Jon and at nights, riding atop his devilish mare, he wrought havoc on Jarl's servants and their homes.
Jon Jarl was liked by his people, but all things must come to an end - and so did his life. His burial in April 1263, after 45 years of his reign, was attended by many guests representing nearly all of the clans of Jorvik. One clan that stood out were his direct descendants, the Silver Clan, whose distant descendants still live in Silverglade. The Great Jarl was buried in a tomb close to the Thorn Rocks, the place where he and his people made their landfall after discovering Jorvik. From there, he would forever watch over his mighty castle in the south. For a more detailed description of Jon's burial see Look for clues in history - book 2.
The access to Jarl's tomb was sought almost eight hundred years later by the druids, who knew of a part of the Light Ceremony Book hidden there.
Star Stable Online
When it's time to collect the druid's copy of the Light Ceremony one of it's pieces is in Jon Jarl's tomb in the moon chamber. That is when the player and Linda meet Jon's ghost, after asking them what they want when he hears it's the druid's copy of the Light Ceremony book piece the pair is asking for. Jon says he'll surrender the book after a test of player's knowledge and allegiance, once all questions are answered truthfully he grants Linda and the player access to chamber.