R'hllor is a prominent god across the narrow sea, but has only a few followers in Westeros. He is also called the Lord of Light, the Heart of Fire, and the God of Flame and Shadow. His symbol is a fiery heart. The followers of R'hllor worship him as the god of light, heat, and life. His enemy is the "great other", whose name is not spoken, the god of darkness, cold, and death.

R'hllor and the great other wage an eternal war over the fate of the world. Followers of R'hllor believe that Azor Ahai, the messianic figure prophesized to return in ancient books of Asshai, will tip the balance of this war. Azor Ahai is also called the Prince that was Promised, the Warrior of Light, and the Son of Fire. Prophecy holds that he will wield a flaming sword called Lightbringer, the Red Sword of Heroes, and raise dragons of stone.

Clergy of the R'hllor religion are called 'red priests,' due to the loose, crimson robes they wear. In the east, children are often given to temples of R'hllor to be raised into the priesthood. Every evening, red priests light fires and sing prayers at their temples, asking R'hllor to bring back the dawn. "The night is dark and full of terrors", is a common phrase in prayers to R'hllor. Priests believe that R'hllor will occasionally answer his followers' prayers by granting magical favors. They often gaze into flames in an effort to see visions of the future. 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.