Forty-one years after the arrival of Saint Seiros in Fódlan, Wilhelm Paul Hresvelg founded the Adrestian Empire, marking Imperial Year 1. It was said that the Empire's name was bestowed by an oracle, and its future blessed by the Goddess. Emperor Wilhelm chose Enbarr as the new nation's capital due to the presence of Seiros.
In Imperial Year 32, Wilhelm raised an army and instigated the War of Heroes with the goal of uniting Fódlan under his rule and ending the tyranny of Nemesis, the King of Liberation. Seiros herself fought alongside the Imperial army.
At some point during the War of Heroes, Wilhelm died and was succeeded by his son Lycaon I, who continued his father's crusade. Over a thousand years later, the people of the Empire revere their founder as Great Emperor Wilhelm I.