Ancestor

The Ancestor is considered by their Church to be the supreme god and parent of the four original tribes of men, and thus of all humanity. The Church believes that when someone dies, they join with the Ancestor, who was there at the start of mankind and waits at the end. This relationship can be symbolized and explained through the Path, a single line that branches out into one giant tree, thereby connecting all people to the Ancestor's tree.

Ancestor Church
The Ancestor is worshipped by the Church of the Ancestor, the state religion of the Empire. The church is headed by the High Priest, who resides in the cathedral in Verity. At the start of the series the incumbent is High Priest Jacob who is later replaced by High Priest Nevis. There are also at least four Archons or regional archbishops, multiple monasteries, and at least six convents including Sweet Mercy, Silent Patience, Chaste Devotion, and Gerran’s Crag.

The Ancestor Church is not the only religion in the empire. The Hope Church is a sanctioned heresy tolerated in small villages, far from the capital. There are also numerous unorthodox order faiths, such as praying to the nameless gods of rain and sun, or praying to the gods of the Missing.

Argatha Prophecy
Many years ago, a Mystic Sister named Sister Argatha made a prophecy that the Ark would one day be opened when "the four tribes demand it with one voice". Many people, including those in positions of authority within the church such as Sister Wheel interpret this line to mean a Chosen One who possesses all four bloods and all the skills associated with each one. Once fulfilled, this prophecy is believed to grant control of the Ark and thus the control of the Focus Moon which would allow the Chosen One to stop the ice from advancing further. It is also said that the Chosen One would have a protector, called the Shield. Although the prophecy is widely believed, Abbess Glass claims that it is fake and simply invented by two Archons just just thirty-five to give the people of the Empire hope. Zole has been assigned the role of Chosen One and Nona the role of the Shield. Other people, notably the emperor's sister Sherzal, interpret the prophesy differently to mean four Shiphearts from each of the four tribes.

Inquisition
The Inquisition is a special branch of the Ancestor Church, outside the normal ecclesiastical control of the High Priest. It is tasked with investigating and rooting out heresy in the Church. The Inquisition is currently headed by High Inquisitor Gamon, but used to be headed by Abbess Glass, known by her previous name High Inquisitor Shella Yammal. Within its ranks are a range of officials such as Senior Inquisitors, Inquisitors, Watchers, and Inquisition Guards.

There is also an ill-defined role called the Prime Instigator intended for a member of the royal family, existing so that the Crown can feel some sense of control over the Church. This role is currently held by the emperor's sister Sherzal. She has redefined the role and taken over the Inquisition to do her bidding. Before her, the Prime Instigator was Juticar, cousin to the current emperor’s grandfather. According to Inquisition records he attended three meetings in thirty-six years.