House Tyrell of Highgarden, is one of the powerful old houses of Westeros. It is currently led by Lord Mace Tyrell, who is appointed as “Master of the Coin” in the small council by Cersei Lannister and is sent to Braavos to negotiate terms with the “Iron Bank.”
His mother Lady Olenna, wields enormous clout in the House Tyrell and is usually the one who calls the shots. His son Loras Tyrell, is a decorated Knight, jailed by High Sparrow for indulging in unnatural sexual behavior and fornication. He was secretly in love with Renly Baratheon as well.
His daughter Margery Tyrell married Renly, but after his death, she married to Joffrey to strike an alliance between Tyrells and Lannisters. After Jofferey’s assassination, she is now married to Tommen Baratheon, but is soon arrested for lying under oath by the church. Despite the controversies at King’s Landing, Tyrells are still the most powerful players in the realm. Here are the 5 reasons why is that so:
They are the rulers of the Reach:
The Tyrells control the most fertile agricultural land in the entire realm. Most of the food and civil supplies of Westeros come from land under the supervision of House Tyrell. Lady Olenna even threatened Cersei Lannister that she will starve out the crown if something happens to her grand-daughter and grandson.
They have a massive Battle-tested army at their disposal:
Tyrells command the largest army in Westeros. In addition, they have a huge fleet of ships from the Redwyne, which is as big as the crown’s fleet. If they really want to dethrone Lannisters, they can get it done in a week or two. They are legitimately powerful.
Lannisters are dependent on Tyrells to retain control at King’s Landing:
At present, there is tension simmering between the Lannisters and the Tyrells, after the arrests of Margery and Loras. The alliance is fragile. Lannisters’ control over King’s Landing is weakened and Tyrells are upset. In the Battle of the Five Kings, it’s the Tyrells which saved the crown from Stannis’s forces invasion.
Daenerys Targaryen needs Tyrells on her side to even dream of sitting on Iron Throne:
Dany is caught up in the east at the moment, in the last scene, she was surrounded by a horde of Dothraki warriors. Once she unites the east, she can begin to march towards Westeros, with a significant army rallying behind her. But if she really wants to sit on the Iron Throne, she needs the Tyrells on her side. As Tyrion told her in season 5, at the moment only Tyrells can be convinced to support her claim.
House Tyrell is one of the richest and wealthiest in Westeros:
They didn’t start out as being powerful or wealthy, but now, they are the richest, in terms of assets or monetary wealth, as Lannisters gold mines have begun to dry up.