The rift between the Grimbles and the future royal family of the Thirty Warrens began on Golden Coast. With King Gerrard left childless by the death of his son, Lord Grimble had aspirations of ascending to the throne. However, Gerrard chose Whitson to succeed him as king, something that Lord Grimble perceived as a mistake and that lift him embittered towards Whitson.
After the Crossing, Lord Grimble became Whitson's most vocal opponent among rabbits, contradicting the new monarch at every turn. Whitson refused to sink to Grimble's level, and even appointed his son as a captain. Unfortunately, the Grimbles continued to cause trouble, with Fleck Blackstar noticing father and son in whispered conference before a voyage across Ayman Lake.
During the winter spent at Halfway Harbor, Whitson had Captain Grimble scout out the River Fay in command of the ship Burnley. During this time the Grimbles secured a fighting among many of the best fighters of the surviving rabbits. They also met and secured an alliance with the Dragons, intending to betray and strand Whitson's followers on an island held by the Dragons. In return, the Grimbles were promised a territory of their own to rule, and received the aid of a Dragon in kidnapping Queen Lillie and stealing the Ruling Stone from Vanguard.
The Grimbles and their followers and allies enacted their plans after Whitson's fleet departed Halfway Harbor. However, Whitson and his followers, aided by repentant deserter Galt, managed to rescue Lillie and escape the Dragons. Captain Grimble and his bucks were defeated and captured, while the Dragons killed a party led by Lord Grimble as punishment for his failures.
Despite the failure of their attempt to establish a new kingdom, the Grimbles would be remembered in Natalia for over a hundred years to come. Over time, some came to believe that the Stone Sword of Flint was lost when they caused the wreck of Vanguard. Another theory suggested that they themselves stole the sacred relic, only to lose it after their plans were thwarted.