The Deorum Mountains are a mountain range that covers almost the entire northern third of Septentionalis. It is a cold, windy, and harsh environment, providing little chance for life to thrive with very few livable, let alone flat areas.
However, the Innovo Imperium managed to build Thronum Dei, the capital of the Imperium, in the southern part of the range in a lush (for the Mountains) valley known as the Vallis Imperium. It is built into the side of a mountain, and the only safe way to get to it is to pass through the Gates of the Imperium at the southern entrance to the Vallis.
The tallest mountain in the range is known as Prima Domus. Supposedly, it is where the Old Gods that created Perpetua first came to the Material Plane to bless Omnes Inum and the people of the Aeternum Empire with their power and knowledge. It is also, supposedly, where the gods left after seeing their gifts abused by the power-hungry pleasure-emperor Lucius Claudius Augustus and his court shortly before the Fracture.
The Innovo Imperium has spent incredible amounts of time, effort, money, and manpower in search of Prima Domus. They hope to find it, scale it, and commune with the gods in an attempt to once again receive their blessing and inherit the power of the Aeternum Empire.