Cregan Stark

Cregan Stark is an unseen character in Game of Thrones. He is long dead by the time of the series. He was a Lord of Winterfell and an ancestor of House Stark.

Background
Cregan Stark once fought with Aemon the Dragonknight, Prince of House Targaryen, member of the Kingsguard and one of the greatest swordsmen of his age, and was only barely defeated.

Season 4
His name is mentioned within the entry of Aemon Targaryen in The Book of Brothers.

In the books
In the A Song of Ice and Fire novels, Cregan Stark's background is the same. Aemon Targaryen afterwards remarked that he never met a finer swordsman.

He was the Lor​d of Winterfell during the Dance of the Dragons and supported Rhaenyra Targaryen's claim to the Iron Throne. It is likely that he was a child during this time since it was his bannerman Lord Roderick of House Dustin who led the northern forces and he would have to be in his prime to face off against Rhaenyra's grandson Aemon who was born well after the civil war.