Religion is always an important part of world-building in fantasy universes, because unlike in the real world, mysticism is more liberal or generous there. their house motto or something about their pantheon.
Suffice to say, there are multiple religions and religious practices in Game of Thrones. So in case some viewers missed what to worship in Game of Thrones, here are the 10 most dominant religions in its fantasy realm.
MOTHER RHOYNE
In Game of Thrones, religions centered around peace and nourishment often overshadowed by bigger religions or cultures. Mother Rhoyne is one such example of this. She's believed to be the goddess responsible for the Rhoyne river, which is the biggest river network in the realm. She supposedly blesses the Rhoyne's waters with nature's bounties, which sustained the Rhoynar for many years.
Too bad the Rhoynar were nearly wiped out by the Valyrians. It is believed that Mother Rhoyne retaliated by flooding one Valyrian city and cursed them with the Grayscale disease.
GODS OF OLD VALYRIA
The Valyrians, Daenerys Targaryen's ancestors, had their own religion before they left their home turf and started conquering Westeros. The Valyrian Gods were quite similar to most polytheistic religions in history, such as the gods in Greek or Egyptian mythology.
Each of them represents an aspect of nature or life that the Valyrians likely needed an explanation for. Regardless of how powerful their pantheon is, it didn't save Valyria from its own doom, and when Aegon the Conqueror overtook Westeros he converted to the Light of the Seven. Still, some places such as Volantis have families that still worship the Gods of Old Valyria.
GREAT SHEPHERD
The Lhazareens are also one of the lesser-known groups from across the Narrow Sea in Game of Thrones, specifically in the continent of Essos. They worship the Great Shepherd. Not much is known about them, but their reputation of being peaceful shepherds precedes them. They still have their warriors and witches though.
The highlight of their during Season 1 as one of the groups that Khal Drogo conquered and enslaved. The "witch" that poisoned Drogo under the pretense of healing him was a Lhazareen woman who broke her priestess vows to get revenge against the Dothraki.
THE BEARDED PRIESTS
The show didn't touch this religion too much, but it had one representative which made quite the presence in Daenerys' retinue: Daario Naharis. In the books, his beard was more majestic and even had an unusual color. That's because he got involved with the Bearded Priests of Norvos.
He even told Daenerys that he was trained to fight like them. The Bearded Priests are a secretive group who rules the city of Norvos theocratically, and their consist of an odd amalgam of warrior-priests. Given Daario's skill in combat, the Bearded Priests are a force to be reckoned with. Their faith, however, is peculiar, as even the people they govern don't know who exactly they worship, just that they represent whoever that is.
THE MANY-FACED GOD
The Many-Faced God should be quite a familiar name by now, especially to Arya Stark, who worships him/her/it for a time in order to become a mystical shape-shifting assassin.
The Many-Faced God is a deity unique only to Braavos. It's followers mainly honor or worship the representation of death in their culture when praying to the Many-Faced God. Their followers believe that only death is the one true god though it can take many forms, making the Many-Faced God both inclusive and violent at the same time.
THE DROWNED GOD
The Drowned God is featured prominently during the episodes involving the Ironborn or the Greyjoys. In that regard, they're an outlier in Westeros for worshipping such a deity. The consecration ritual of the Drowned God religion involves drowning and resurrection.
That's why any king in the Iron Islands gets drowned and resuscitated before getting the respect of his followers.
THE GREAT STALLION
The Dothraki are no doubt heavily influenced by Mongolian hordes led by Genghis Khan, and are famed for their skill in mounted combat. That's why it's only fitting for the Dothraki god to be a horse, specifically the Great Stallion.
For the Dothraki, this Great Stallion represents the strength of their culture as they owe a lot to horses. Given how vast the Khalasars are, it's safe to say that this is one of the most mandatorily popular religions in the continent of Essos.
THE RED GOD/THE LORD OF LIGHT
As one of the most prevalent belief systems in Game of Thrones, the Red God, or otherwise known as the Lord of Light or R'hllor, is a religion that believes in a prophesized messiah.
Followers of the Lord of Light also only answer to red priests as official clergies of the religion, the most notable of which is Melisandre. The Lord of Light also seems to be one of the most transparent and present gods in the show, likely resurrecting Jon Snow and Beric Dondarrion.
THE OLD GODS
Also known as the Old Gods of the Forest, this religion is a pantheon of countless nature spirits. They are the dominant belief system in the North of Westeros, from beyond the wall to the Starks' dominion. It closely resembles paganism in the real world.
They have no official temples, but still pray to trees in their godswoods, which have a weirwood heart tree in the center. The Children of the Forest were the ones who carved faces on the weirwood trees and made them designated worship areas. It's not just the Northmen of Westeros who worship them, but Wildlings and other races beyond the Wall.
THE FAITH OF THE SEVEN
Last but not least, the most popular religion in the Seven Kingdoms of Westeros, the Faith of the Seven. They consist of seven gods, each representing different values and walks of life. Followers of the Seven believe that while they do only have a single god, it is divided into seven different aspects, sort of like the Holy Trinity.
They're also called the New Gods, and the vast majority of the kingdoms subscribes to this particular religion.