The Fifteen Houses

This information was gleaned from exploration of the Thrusian Cemetery, interrogation of various head priests of the Thrusian Cathedral, and conversations with Samuel.

In antiquity, before the Draconic Empire but after the advent of the races, mortals of significant power began ascending to Godhood. At that time as far as what is known there was only one god, the Dagda. These mortals started becoming gods, but with each ascension it became harder for others to ascend. Finally, there was a set of fifteen gods, including the Dagda, and no others were able to ascend.

Flash forward to the time after the fall of the Draconic Empire. Fifteen individuals of great power were identified as Gods on Earth; eight refused this mantle and seven embraced it. There was widespread war between the seven until a simple farmer gathered an army and overthrew them all (the ancestor of Aramus).

Several generations later Aramus gathers an army and succeeds in uniting most of the continent. He establishes a new nobility initially based on merit, the fifteen houses of the Thrusian Cemetery are part of this nobility.
These houses are descended from the fifteen ascended gods. They all have generations in the Year of the Ram, the year that the divine aspect is supposed to manifest. Of the fifteen houses it is speculated that six were absorbed into other houses creating a perchance for twins during the Year of the Ram. One houses remains pure, and two houses have died out.