R'hllor, The Lord of Light

Background
R'hllor, also known as the Lord of Light, the Heart of Fire, the God of Flame and Shadow,[is a prominent god in 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. Red priests lead prayers to R'hllor at red temples.

Timeline Post-300 AC
301 AC:  High Priests of the Red Temples acknowledge Stannis Baratheon and Melisandre have managed to stay the coming of the Long Night, for now. But they see in the flames the threat will reemerge yet again.

302 AC: Still convinced that Daenerys and her fiery beasts are instruments of the Lord of Light, Benerro pressures the Volantene Triarchs to accept the Targaryen Queen into the city. Moqorro completes his quest to unite Daenerys with Victarion’s Iron Fleet. The Red Temple anticipates great achievements from the Mother of Dragons.

330 AC: The return of dragons to the world has greatly aided the recruitment of followers of R’hllor. Modest Red Temples throughout Essos are slowly being upgraded to great Temples of the Lord of Light. The strength and influence of R’hllor has never been greater.

352 AC: It has been seen in the flames the Others are once again are gathering their strength. Benerro and the Volantene Red Temple support the Targaryen invasion of Westeros, hoping a Targaryen monarchy will be more receptive to the threat up North.

355 AC: With the last dragon perished, the popularity and strength of the faith of R’hllor has begun to dwindle. In turn, the Temple of the Lord of Light has ceased its support of the Targaryens.

365 AC: The magic that has kept Benerro alive for so long, has begun to lose its potency. Ostensibly, he remains the High Priest of the Red Temple of Volantis, but he has not been seen preaching in public for several years. It is unclear who truly leads the influential Volantene temple.

366 AC: Upon Daeron Targaryen’s full conversion to the Dragon Gods of Valyria, Red Temples throughout Essos have begun to preach against the Targaryens, fearing the rogue religion will usurp its followers.

370 AC: The influence of the followers of R’hllor has fallen to match pre-300 AC levels. Several great temples to the Lord of Light have fallen to a state of disrepair. But it has been seen in the flames the Others are beginning to mobilize, therefore, Red Priests throughout Essos have redoubled their efforts to recruit and convert followers.