R'hllor

R'hllor, also known as the Lord of Light, the Heart of Fire, the God of Flame and Shadow, is a prominent god on Essos, but has only a few followers in Westeros, where he is more commonly known as the Red God. His symbol is a fiery heart.

Beliefs
The religion is based on a dualistic, manichean view of the world: R'hllor, the god of light, heat, and life, and R'hllor's antithesis the Great Other, the god of ice and death. They are locked in an eternal struggle over the fate of the world; a struggle that, according the ancient prophecies from the books of Asshai, will only end when Azor Ahai, the messianic figure, returns wielding a flaming sword called Lightbringer, the Red Sword of Heroes, and raises dragons from stone. According to Martin, this faith is roughly based upon the fire worship of Zoroastrianism. This religion's dualistic aspects of a good and an evil god are also inspired by Zoroastrianism, along with the Cathars of Medieval Europe who were annihilated during the Albigensian Crusade.

Clergy
Clergy of the R'hllor religion are called "Red Priests", due to the loose, crimson robes they wear. Red priests may be male or female. In the east, they are a common sight, where the faith of R'hllor's influence is more widespread and children are sometimes given to temples of R'hllor to be raised into the priesthood. The temples, often called "red temples", also buy children as slaves who are known as Slaves of R'hllor and raise them as priests, temple prostitutes, or warriors. The warriors that protect the greater temples are called the Fiery Hand.

Known red temples

 * the red temple in Pentos
 * the red temple in Braavos
 * the red temple in Lys - according to semi-canon sources, one of the greatest temples of R'hllor stands in Lys.
 * the red temple in Selhorys
 * the red temple in Volantis
 * a small red temple in Oldtown for the sailors who visit there.
 * there may be a red temple in Dorne (suggested by Obara Sand)

Known Priests of R'hllor

 * Benerro, High Priest of R'hllor of Volantis.
 * Thoros of Myr
 * Moqorro
 * Melisandre of Asshai
 * Ezzelyno

Rituals
Every evening, red priests light fires and sing prayers at their temples, asking R'hllor to bring back the dawn. Followers often gaze into flames in an effort to receive visions of the future. It is believed that R'hllor will occasionally answer the prayers of his followers by granting visions and abilities such as raising the dead. The priests of R'hllor also seem to be able to evoke fire with their bare hands and be able to control it to attack enemies or simply to impress common people. Some rites performed by the red priests include sacrificial immolation. According to Melisandre, R’hllor speaks to his chosen ones through blessed fire, in a language of ash and cinder and twisting flame that only a god can truly grasp.

Trials by combat are an accepted practice in the R'hllor faith; prayers before the combat ask R'hllor to give strength to the just party. "The night is dark and full of terrors", is a common phrase in prayers to R'hllor.

History
The worship of R'hllor is a religious tradition on the continent of Essos, but has not gained much popularity in Westeros. Recent efforts to spread the faith to Westeros include the red priests sending Thoros to King's Landing to convert the fire-obsessed Aerys II. This attempt failed after Thoros was unable to impress Aerys with his fire magic.

Like other types of magic, the magic of R'hllor seems to have faded after the last Targaryen dragons died, but with the return of the dragons in the east, the abilities of R'hllor priests have strengthened. Thoros, while serving at the temple in Myr, did not experience any form of new-found powers. However, since the return of the dragons he has resurrected Beric Dondarrion during a traditional R'hllor burial ritual. Melisandre's powers have been augmented since her arrival at the Wall.

Recent Events
Two new circles of worship formed in Westeros, following red priests of R'hllor. Thoros and Beric founded the Brotherhood Without Banners, an outlaw organization bound in part by their worship of R'hllor. At Dragonstone, Melisandre wielded fire magic and convinced Stannis Baratheon to claim the mantle of Azor Ahai. However, after the final death of Beric and the defeat of Stannis at the Blackwater, Thoros and Melisandre's influence over their congregations waned.

According to the High Septon, Lord Stannis has turned from the truth of the Seven to worship a red demon, and his false faith has no place in the Seven Kingdoms.

In her newly conquered city of Meereen atop the Great Pyramid, Daenerys Targaryen contemplated the gods and thought about religion. She recalled that the red priests believed in two gods, she had heard, but two who were eternally at war. Dany does not like the sound of that. She thinks to herself that she would not want to be eternally at war.

In Qohor, the followers of R'hllor tried to burn the Black Goat.

In Volantis, Benerro preaches that Daenerys Targaryen is Azor Ahai reborn and encourages many to support her.