Warlord rule barring dismantling of a captured headquarters that doesn't border your land, leaving it exposed to recapture.
The instant the Prism Kingdom's assets pass to The Princess Posse, a Warlord Message tells Carl he owns non-adjoining property and therefore may not dismantle this headquarters. The Throne Room is declared vulnerable to attack, and if it is taken he loses all the land associated with the former Prism team.
The rule turns a total victory into a defensive problem: Carl concludes he cannot hold the position, orders the gnolls to strip the castle of loot, and declines Boomer's suggestion to push on toward the Blood Sultanate Castle.
Turns captured enemy headquarters into an undismantlable liability that can bleed away conquered territory.