How these religious fanatics became huge players on 'Game of Thrones'

Helen Sloan/HBO

Warning: Spoilers ahead for "Game of Thrones" season six.

Sunday's "Game of Thrones" episode made it clear the High Sparrow and Faith Militant are powerhouses in King's Landing, and won't be going down without a fight. The High Sparrow played good-cop with Margaery, while Cersei and Tommen plotted ways to destroy him. But it won't be easy.

So how did the High Sparrow manage such an effortless power grab? It may be surprising to see the High Sparrow and his faith-driven army go up against Cersei and Tommen for some viewers, especially given how ruthless we know Cersei can be. 

Turning to the books for more context will help — especially when you realize how much support the High Sparrow has from the common people of Westeros.

In the books, readers are given several point-of-view chapters that take place in the Riverlands. This area of Westeros was particularly devastated by the War of the Five Kings between Joffrey Baratheon (Lannister), Robb Stark, Renly, Baratheon, Stannis Baratheon, and Balon Greyjoy. Large swaths of the Riverlands were burned, wrecked by battles or roving bands of Lannister soldiers who pillaged, raped, and killed at will. 

The show gave a peek at this through Arya's season four journey, as she and the Hound stumbled upon many inns and farms in ruin, their owners dead or dying.

Helen Sloan/HBOSo when septons (religious leaders of the Faith of the Seven) were being killed, and devout followers of the Faith watched as their homes were ripped apart, it was only a matter of time before the commoners became disillusioned with their king. 

So, along comes the High Sparrow. In the books we're given hints here and there that a group of radical religious people are coalescing, all with the intention of supporting and protecting the poor and reversing the devastating effects of the war. Then the existing High Septon in King's Landing is killed, and a group of clergy gather to select a new leader, not unlike the way new popes are chosen in the real world.

But — the High Sparrow and his followers essentially storm the selection meeting and force the committee to choose the High Sparrow as the new High Septon. 

Helen Sloan/HBOThe previous High Septon was a fan of comforts — jewels, fancy clothing, nice food, and the like. When the High Sparrow took over, he immediately sold the Faith's valuables in order to raise funds. This money was then used to feed and clothe the poor. These actions won favor with the commonfolk, while Cersei and the royal family began to look more and more selfish and uncaring of the people in their realm.

Cersei, short-minded as she is sometimes, sees the High Sparrow and his followers as a nuisance — not a threat. But she is at least aware enough to realize she needs their help. In the books, it's clear to Cersei that she needs this new High Sparrow to publicly support Tommen's claim to the throne, especially amid the (true) rumors that he is a bastard born of incest. 

Plus, in the books, the crown has a huge monetary debt owed to the Faith. Having the High Sparrow on her side would help mitigate that problem. So what does she do? Cersei gives the High Sparrow an army. 

In the show, Cersei's motivation to arm the Faith Militant seems to come only from her desire to lock Margaery in prison. Either way, it's a bold move that comes back to bite Cersei. 

Helen Sloan/HBOThe Faith Militant is a military branch completely controlled by the High Septon (or Sparrow) and devoted to the Faith of the Seven and carrying out the gods' justice. They haven't been an active group for over 200 years, however. 

Cersei's move to re-instate the Faith Militant was an impulsive decision which winds up handing far more power to the High Sparrow than she initially realizes. With the royal decree in place, the Faith Militant has the ability to put the crown in check — which we've seen play out in the imprisonment of both Cersei and Margaery (in the show AND in the books). 

Cersei obviously thought she could manipulate the High Sparrow, but ultimately underestimated his devout faith.

Helen Sloan/HBONow there's little Cersei and King Tommen can do to usurp the High Sparrow. At least, not without having the common folk rebel against them entirely. The High Sparrow's immersion with the poor (who are numerous) puts Cersei in a bind. Sure, she and Tommen could incite a full-blown war against the Faith, but the religion of the Seven is widely practiced in southern Westeros. Going against the High Sparrow would be political suicide. 

Book readers aren't completely sure what the High Sparrow's endgame is, aside from purging King's Landing of those less committed to the Faith and more intent on selfish power and riches. 

Based on Sunday's episode and the conversation between Olenna Tyrell, Cersei, Kevan, and Jaime, we'll see a clash of armies soon. Cersei plans to have the Tyrell army invade King's Landing in order to stop Margaery's "walk of shame." Viewers can't be sure that this is all Cersei wants. After all, altruism isn't her greatest strength. But the fight between the rich houses of Westeros and the High Sparrow will be interesting to watch nonetheless.

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