Gorne as depicted in Game of Thrones: Histories & Lore.
Maester Herryk's History of the Kings-Beyond-the-Wall transcribes how Gendel and Gorne were asked to mediate a dispute between a clan of children of the forest and a family of giants, who argued over the ownership of a cavern. Gorne and Gendel eventually used trickery to resolve the issue, after discovering the cavern was part of a chain of caverns that passed beneath the Wall. According to Maester Herryk's history, Gorne and Gendel made both the giants and the children swear no longer to desire the cavern.
The passage underneath the Wall became known as Gorne's Way. In search of conquest, Gorne and Gendel led the free folk south through Gorne's Way, allowing them to evade the Night's Watch. Gorne and Gendel fought against the King in the North, and Gorne killed the King in the North. However, the king's son took up his fallen father's crown and killed Gorne. According to northern stories, Gendel died as well, although both maesters and wildlings claim Gendel survived the battle and led the survivors back underneath the Wall to the lands north of the Wall. However, not knowing the caves as well as his brother had, Gendel became lost, and none of his people ever emerged.