Religion has always played a principal role in George R.R. Martin's world of Ice and Fire, with most of Westeros worshiping the Faith of the Seven, while Northerners like the Starks pray to the Old Gods. But now, with Cersei going to war with the High Sparrow and his pious fundamentalists in King's Landing, religion has become an increasingly important theme this season on Game of Thrones too.

Red priests have popped up in Meereen, Arya has been training to become a lethal follower of the Many-Faced God, and Jon Snow was resurrected from the dead by the red priestess Melisandre, who worships R'hllor, the Lord of Light.

With a menagerie of deities in the Game of Thrones saga to digest, we're here to help you sort it all out. Why was Ned so fond of sitting in front of that tree? Why did the White Walkers leave those morose symbols in the snow? What are the many faces of the Many-Faced God? Why does Melisandre love setting people on fire? Let's delve into worship in Westeros and find out.

The Old Gods of the Forest

Before the First Men arrived from Essos thousands of years ago, Westeros was inhabited by the Children of the Forest. They worshiped the Old Gods, deities that had no names and manifested in trees, rocks, and streams. There were no temples or priests in the traditional sense. However, greenseers, or those with the magical ability to perceive future, past or distant events in dreams (like the Three-Eyed Raven and Bran Stark), were highly respected by the Children of the Forest.

In the show, this religion is often symbolized by sacred weirwood trees, and when you cut such trees, they appear to bleed. Before the First Men arrived, the Children of the Forest carved faces into the weirwoods, so that the Old Gods could watch over them. The First Men eventually accepted these gods, which is why the Starks of Winterfell have worshiped them for thousands of years. The Old Gods of the Forest are largely worshiped in the North and Beyond the Wall.

While it's unclear if the White Walkers worship the Old Gods, or any gods, they were created by the Children of the Forest, and as a result, they've been known to recreate some of the ancient symbols used in their rituals ... with severed heads and human body parts. Fun!

The Faith of the Seven, or the New Gods

The Faith of the Seven is the predominant religion in the Seven Kingdoms. Spurred by visions of a "Seven-faced god," the Andals invaded Westeros, where they overran and conquered most of the continent from the First Men. The Andals brought with them their own religion, the Faith of the Seven, which is also referred to as the New Gods. They also overtook most of Southern Westeros, but failed to claim the North, which is why most Northerns still worship the Old Gods.

After Bran's accident in Season 1, Catelyn Stark (née Tully), who originally hailed from the Riverlands in central Westeros, used her homemade prayer wheel to pray to the Seven. Most people in King's Landing believe in this religion, in which everything is built around seven facets of one god: Father, Mother, Warrior, Maiden, Smith, Crone, and Stranger.

Currently, the Faith of the Seven is at the forefront of the turmoil in King's Landing, as the High Sparrow's militant faithful currently have free rein to wipe out any and all sin they see. They're implacable. The Sparrow's pious devotion has divided the people of King's Landing, many of whom feel abandoned by the crown and ready to see the nobles pay for their sins.

The Lord of Light (R'hllor)

Martin named his series A Song of Ice and Fire, and perhaps no other is religion is tied as closely to the ethos of Game of Thrones as The Lord of Light. R'hllor, a fire god, is known as the "one true god" in many parts of Essos, particularly the Free Cities. Melisandre worships the Lord of Light, and in doing so, she also believes that all other gods are demons and must be destroyed. Occasionally, those faithful to the Lord of Light will even kill nonbelievers and they're known to make blood sacrifices to their deity. (R.I.P. Shireen Baratheon.) Followers of R'hllor also believe in "the Prince That Was Promised" -- essentially a second coming of legendary figure Azor Ahai -- who will once again save the world from disaster. (We're looking at you, Jon Snow.)

The priests and priestesses of the Lord of Light are known to be extremely powerful. Melisandre uses fire in many of her rites, such as throwing leeches into open lames while reciting the names of the “three false kings.” (All of whom are dead now.) It was revealed in the Season 6 opener that Melisandre has been using a spell, known as a glamor, to conceal her real appearance for centuries. She also resurrected Jon Snow from the dead and birthed a murderous shadow baby. The Lord of Light is looking pretty legit.

The Drowned God

The Drowned God is the deity worshiped on the Iron Islands. Unsurprisingly, they believe their god lives under the sea, which is totally normal because that's where their heaven is, too. The Ironborn don't fear the sea or drowning because as it's previously been established, "What is dead may never die." Drowning is kind of like a right of passage for the Ironborn. All infants on the Iron Islands are ceremonially "drowned" during a baptism rite by being briefly submerged in sea water. When Theon Greyjoy returned to the Iron Islands, his father Balon made him get baptized again out of fear that the Starks had converted him to the Old Gods. When Euron Greyjoy was anointed King of the Iron Islands, the Drowned Man (or priest of the Drowned God) purposefully drowned him.

Followers of The Drowned God believe he created the Ironborn to reave, raid, and pillage. Better yet, killing one's enemies in battle is considered a pious act. So, technically, Euron, with all of his faults, is a man of god.

The Many-Faced God

Though a minor religion in Braavos, the Many-Faced God, also known as the God of Death, is worshiped by a cult of assassins known as the Faceless Men. They are Death's humble servants. However, this God of Death has many faces. The Faceless Men believe that devotees of every religion worship death, as every sect has its own god of death -- and these gods represent the "faces" of the Many-Faced God. The Faceless Men also see death as a gift from their god; one meant to end human suffering, just as it's considered a gift to end the lives of those who are causing suffering to others.

Can't get enough of Game of Thrones? Listen to this week's Game of Crones podcast, featuring MTV News pop culture writers Teo Bugbee, Leah Beckmann, and yours truly, Crystal Bell.