The first Tower Realms were raised by the Priest Kings. Tower Realms celebrate the vertical power embodied in class societies. All this power is channeled into building, expanding, and reaching up to Heaven. To become gods or at least like the gods.The Priest Kings sought to challenge Heaven. This single end always breeds isolation and amplifies arrogance.
All too often, the gods take their revenge.
Lightning strikes twice in the Tower Realms - again and again. Tower Realms almost always meet their end in a sudden, explosive way. Great Kings and Queens, Grand Architects and Viziers fall to their deaths as their Tower Realm disintegrates underneath and around them on all sides. This is often the fate of the workers toiling to build the Tower as well.
The fall usually begins subtly. New words - even nonsense words - enter a Tower Realm's vocabulary. Language becomes confused. New languages emerge among the Builders and their workers. Treaties are not properly honored because promises are twisted or misinterpreted. Trade relations break down. Alliances falter. New insights occur among the populace, and philosophical, religious, or political revolutions come out of nowhere. The foundation shatters. The Tower falls.
A few remain behind, mining and recovering treasures from inside the ruins.
"Look on my works, ye Mighty, and despair!"