It began when the cities fell. The Aldmeri Dominion claimed that Alinor, the jewel of the Summerset Isles, nay, the jewel of Tamriel, would never fall like the other cities. But the doubts grew as more cities were conquered, too fast for any normal army to believably accomplish. The rumours began to spread. Some claimed that these victories were due to the Tribunal assisting the conquests, others claimed that there was a secret army of immortal warriors. All of them were proven wrong. The Aldmeri Dominion quashed all inklings of the truth. It knew what it was fighting, and knew they had only the barest chance of winning, but they hid the truth to prevent a panic, for if the citizens knew the enemy controlled a god, they would lose all hope.
The god was sighted, slowly walking towards the city. The greatest mages in the lands threw mighty spells, capable of destroying fortresses, but it didn't even stagger. It reached the walls of the city, and with only its hands tore them apart. The skies constantly switched between day and night. Strange warriors wearing armour resembling the most ancient elven designs futilely attempted to destroy the bronze colossus. Strange vessels in the sky were occasionally seen firing bolts of energy at the giant, with several missing and hitting the citizens below. The brass god continued walking, spreading chaos as mysterious elven armies from the past and future futilely attempted to stop it. The god-machine stopped at the greatest palace of Alinor, where the leaders of the Dominion trembled in fear. It forced its hands through the walls, and tore the building apart. In a few moments, the entirety of the upper echelon of the Aldmeri Dominion were killed. The brass walker turned and reached towards the Crystal Tower.
The Imperial Battlemage received a dreamsleeve message a short while after the destruction of the palace. The contents were simply "Stop it! We beg for mercy! All our lands are yours, just spare us!" Numidium paused just before its hands touched Crystal-Like-Law, and walked away from the smouldering ruins of Alinor. In five hours, it had destroyed almost all of what was formerly one of the largest cities in all of Tamriel. Thus, Tiber Septim finally conquered all of Tamriel. The temporal echoes of the siege are still felt to this day, and the Thalmor still try to quell them.
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I didn't think I did a good enough job of describing the time-breaking effects of the Brass Tower. Oh well. Anyway, I hope you all enjoyed my portrayal of the Siege of Alinor.