The Allagan civilization thrived within the borders of a vast empire, producing marvels the likes of which this world has never seen again. It's said that its technology was so advanced, the magitek of Garlemald appears crude and childlike in comparison. When I first laid eyes on the Crystal Tower, I finally realized the truth of that claim...
The Allagan Empire, or just simply Allag, was a historical empire in the backstory of Final Fantasy XIV. It had expanded all across Eorzea and beyond during the Third Astral Era. Its technology remains unsurpassed—the modern Garlean Empire's magitek is described as child's play in comparison.
Among Allag's creations are Dalamud, the Crystal Tower, the Ultima Weapon, the Diablo Armament, and Azys Lla. Other relics, such as tomestones, remain popular in modern times as collectors' items. The Sons of Saint Coinach is an organization from Sharlayan dedicated to researching the ancient civilization.
The Allagan Empire was founded by Emperor Xande under the influence of the Ascian Emet-Selch during the Third Astral Era, five millennia before the events of the main story. Through both the Ascians teaching the means to bind primals to the physical world, and the discovery of Omega 150 years after Xande's death, Allag's mastery over aetherochemistry allowed it to bioengineer chimeras and other biological weapons while also building space-faring vehicles.
While Allag had encompassed most of the world at the peak of its reign with an innumerable populace under its sway, it stagnated due to a lack of strong leadership and the complacency brought on by post scarcity. To restore it to prosperity, a technologist and magician named Amon sought to revive Xande to provide the empire with a strong leader for eternity. Amon cloned Xande's descendants, Doga and Unei, who would eventually imbue their clones with their will. The reborn Xande returned the Allagans to their former glory.
Xande was dissatisfied as he had never fulfilled his original ambitions of conquering the entirety of Hydaelyn. Thus, he sought the forbidden power of darkness: the voidsent. Since the Crystal Tower itself could not generate the power to maintain a stable portal to the Realm of Darkness, Xande had the Elder Primal Bahamut placed in the artificial moon Dalamud to harness the solar energy needed to enable the dark covenant.
Xande's conquests and the resurgent spread of the Allagan Empire led to discontentment, and it is implied numerous uprisings took place in the empire's final days. In an act of desperation, Xande attempted to transfer Dalamud's full power into the Crystal Tower to complete his pact and tear open a rift to the World of Darkness. It was too much for the tower to maintain as excess energy escaped into the ground, resulting in a catastrophic earthquake that devastated most of Allag while ushering in the Fourth Umbral Era as the Ascians had planned from the beginning.
With the Crystal Tower buried, the civilization that had become reliant on its energy plummeted into chaos. Though Allag and its culture faded, their relics remain scattered across Eorzea.
Military and technology
By the end of the Third Astral Era, the Allagans phased out conventional soldiers in favor of artificial creatures and machines. Due to Allag's highly advanced technology many of their vessels looked nothing like modern airship designs, typically resembling either globular vehicles, such as the Fractal Continuum and Dalamud, or in the case of Ragnarok-class starships, gigantic swords. The flagship at the heart of Azys Lla resembles a towering spire with a flattened top deck.
The Allagan scientists' mastery of aetherochemistry allowed them to manipulate life itself. Once such process was cloning, which a resurrected Xande used to streamline the human sacrifices needed for his covenant with the Cloud of Darkness, even using clones of himself.
Allag synthesized chimeras through alchemically "marrying" various dissimilar creatures that included wildlife and dragons. The experiments were a dead end prior to being perfected in the Fourth Generation, with some of the resulting creatures having sapient races in their composition. Some chimeras were also created using voidsent parts, like with the nagas. Many of the chimeras fled into the wild following the Fourth Umbral Calamity with the Eorzeans having believed they were natural wildlife until the Seventh Astral Era. Some Beast Tribes, like Ixal, are related to the Iksalion chimeras of Azys Lla.
Allag's greatest achievement may have been the binding of primals, an ability they learned from the Ascians. The Warring Triad were sealed as a power source for Azys Lla, while the primal form of Bahamut was incarcerated in Dalamud as an orbiting satellite. Some of these anti-primal systems may have been using even older artifacts, as Lahabrea implied the Heart of Sabik with the Ultima Weapon's core predates the Allagan civilization. The Eorzeans also assumed that Omega was an Allagan Weapon since the empire reverse-engineered the alien entity's technology. According to the Fractal Continuum, Void research was an "emerging field" late in the Allagan period, with the Diablo Armament intended to harness Diabolos' power.