The White King is the king of Prospit, and can typically be found leading his troops on the battlefield. In his fully-prototyped form, he towered over nearly all forces on the battlefield. However, following the request of the Parcel Mistress, he, like the White Queen before him, abdicated his position and turned his scepter over to the Parcel Mistress. Upon relinquishing his scepter, his stature was reduced drastically, leaving him around the same height as the Parcel Mistress.
He somehow ends up in the Frog Temple and enters the Lotus Time Capsule spawning a second blooming, the first holding Dave's copies of Sburb to be retrieved by Jade in 2009. He later emerged from it in 2422. Before entering, he reads Complacency of the Learned and seems interested in it. His new exile name is Writ Keeper, which has the same initials as White King.
On exiting the Capsule, he is welcomed by the Windswept Questant - and then murdered by Bec Noir, shortly (about ten seconds) after Noir's exit from his own Capsule.
While the White Queen seems to generally take care of ruling Prospit on the home front, the White King is on the battlefield, leading the troops against the forces of Derse and the Black King. What he does in times of peace is unknown, if there are indeed times when Prospit is not embroiled in conflict with Derse.