When Joffrey Baratheon was poisoned in the “Purple Wedding” orchestrated by Lady Olenna and Little finger, the throne was passed to the next in line Tommen Baratheon. Joffrey was a coward but brutal, he ordered to behead Lord Eddard Stark to send a message to the entire Westeros on how the crown’s enemies will be treated. King Robert was a terrible administrator but he won the war against the Mad King, you can’t take that away from him. But since he took control, he hasn’t once played Game of Thrones to outsmart his enemies. He has been an empty vessel where anyone can pour thoughts and he will parrot it out.
High Sparrow has literally become the new “power center” at King’s Landing now, he is riding on a high horse believing he is the messenger of mighty Gods. He arrested his brother-in-law Loras Tyrell, Queen Margery for withholding the information and his mother Cersei Lannister on charges of fornication. He made her go through Walk of Shame, while King Tommen remained a mute spectator of the events.
High Sparrow has twisted Tommen in a way that he feels his actions are god’s will. He didn’t allow his mother to attend the funeral of Myrcella in the Sept. He came out in the open and announced a pact with the church to prevent Margery’s Walk of Shame (apparently he had no issues with Cersei’s humiliation). He ousted Jaime Lannister as a member of his Kingsguard and sent him to Riverlands to safeguard crown’s interests. He, in fact, has replaced his entire Kingsguard with the order of the faith militant called “Warrior’s sons”. They are the higher noblemen who renounced their titles and joined the faith militants. One can see on their breastplates, there is a seven-pointed star instead of House sigil. He is totally surrounded by faith militant troops now, which makes him beyond the influence of Cersei Lannister. He is almost brain-washed by High Sparrow who has established a theocracy in Westeros and wields more power and clout than the small council. Will there be a comeback of sorts of King Tommen?
