Getting to know 5th Edition
Rule of the High Thane
Though the Dwarf towns and strongholds of the northern Ice Mounts have always quarreled amongst themselves, it was decided that a High Thane would be crowned to lead the entire kingdom against outside enemies, whether that was from the Humans and orcs of the surface or the viler races that populated the Underdark. Though the thanes of each stronghold held power, they ultimately would bow to the high thane's commands in times of war. This allowed the nation to band together during the God War and drive off the attack of Salarax the Fleshless during the Year of Flame.
However, during the Earthbreaker War, the high thane was killed in a battle with the Elfves of Quendayar. His heir was rushed to the Hallowed Vaults to be crowned, but infighting among the dwarves resulted in the heir being captured by a rogue stronghold and held for ransom. This launched the dwarves into chaos that lasted for decades and it was during this time that the Vaults were destroyed by an underdark army led by the drow (see Dark Elfes). Now without king or throne, the dwarves broke back into the fractured city-states that they are today.