An Expansion available to all factions from the start of the game. Constructing the Altar of Auriga is required to unlock Blessings, as well as voting on the effects of the next winter. As such, the Altar of Auriga must be built before Pearls can be used for anything aside from diplomatic trade, or building the Garth of the Allayi for the Allayi.
Although the Altar of Auriga can only be built once in your empire, it is possible to obtain multiple Altars by conquering cities of other empires where the Altar has already been built. However, this doesn't grant any kind of special bonus aside from the FIDSI output the Altar provides.
The Altar of Auriga is a sacred building to those who live upon her. It is a center of ancient power from the times even before the Endless. By bringing her Pearls here and unlocking the Altar's Blessings, powerful magical effects can be applied to a city, region, or empire.