Lord Mace Tyrell is the Lord of Highgarden and head of House Tyrell. He is the father of Loras and Margaery Tyrell, and the son of Olenna Tyrell. He initially supported Renly Baratheon's claim to the Iron Throne in the War of the Five Kings, but after Renly's death he successfully negotiated an alliance with House Lannister to support King Joffrey's claim to the throne, on the condition that his daughter Margaery would marry Joffrey, making her the new queen and giving House Tyrell the prestige of entering into the royal bloodline.
Mace Tyrell is the Lord of Highgarden and head of House Tyrell, one of the Great Houses of Westeros. He is the Lord Paramount of the Reach and Warden of the South. The Tyrells are one of the richest and most powerful families in Westeros, second only to the Lannisters - for while the mountains of the Westerlands possess rich gold mines, the fields of The Reach are the most fertile in Westeros, capable of supporting armies almost twice the size of any other kingdom.
Mace is not considered a great strategist or general himself - his own mother Olenna openly describes him as an oaf. On the other hand, he has shown good judgment in delegating such tasks to trusted, skilled subordinates, such as the famous general Randyll Tarly, who often commands Mace's forces in battle.
Mace might not be the most intelligent man, but he is an amiable fellow well-liked by most of his bannermen, as well a loving husband and father. Mace has one son, Loras, and a daughter, Margaery, arguably the most eligible woman in the Seven Kingdoms. Mace hopes to make a good match for her to increase the already considerable power and influence of his family. Mace is particularly eager for Margaery to secure a royal marriage for their family because unlike some of the other Great Houses of the Seven Kingdoms such as the Starks or Lannisters, the Tyrells never ruled as kings in their own right, but were granted control of the Reach as a reward for submitting to Aegon the Conqueror during the Targaryen Conquest three hundred years ago. Thus entering into the royal bloodline would increase House Tyrell's prestige and secure their rule over their fractious vassals in the Reach.
During Robert's Rebellion, Mace and House Tyrell stayed loyal to House Targaryen. The Tyrells owed their rule over Highgarden and the Reach to the Targaryen kings, who after the Targaryen Conquest three centuries before had awarded rule of the Reach to the Tyrells ahead of other families from the region which actually had better claims (such as House Florent). The Tyrell armies were able to inflict the only defeat that Robert Baratheon suffered during the entire war at the Battle of Ashford. Afterwards, Mace's massive army moved east to lay siege to the mighty castle-seat of the Baratheons, Storm's End. The Siege of Storm's End lasted the better part of a year, while Mace and his commanders feasted in sight of the starving garrison led by Robert's younger brother Stannis. Ultimately Stannis's determined defense held, and the siege only succeeded in pinning down Mace's army and preventing it from assisting the Targaryens in the climactic battles occurring further north. After the Sack of King's Landing, Eddard Stark rode south with the main rebel army to relieve the siege. With the capital city in rebel hands, and both Prince Rhaegar Targaryen and his father Mad King Aerys dead, Mace saw that the war was clearly lost and gave no battle to Lord Eddard. Instead he peacefully dipped his banners and submitted to Robert's rule, and in return was treated leniently, pardoned, and allowed to continue ruling the Reach as his family had before the war. However, ever since there was never any great love between Mace Tyrell and Stannis Baratheon.
Ser Loras tells Renly that his father would support Renly's claim to the Iron Throne. Renly rejects the notion, pointing out he is fourth in line to the throne, but Loras explains that he could fight for Renly and his father would bankroll their armies. Renly seems more intrigued by the notion and later accepts the plan, though he fails to win the support of Lord Eddard Stark. Along with Loras, Renly flees the city of King's Landing and heads south towards the Tyrell homelands. It is later reported that Renly has been crowned king, with the full support of Lord Mace Tyrell and his forces.
Davos Seaworth mentions to Stannis Baratheon that Lord Mace is amongst the many lords that have declared for Renly Baratheon
After Renly's death, the Tyrells enter into a new alliance with King Joffrey and House Lannister, instead of siding with Renly's brother Stannis, who is correctly suspected of having something to do with Renly's death.
Lord Mace is mentioned by his mother, Lady Olenna Tyrell, in conversation with Sansa Stark. She describes him as "a ponderous oaf" who rushed into a treasonous alliance with Renly and a dangerous one with the Lannisters just to see his daughter become queen.
Lady Olenna mentions him again some weeks later when in the Great Sept of Baelor with Cersei. She says that Mace enjoys hunting because it hides the fact that he's never been in a real battle. Cersei expresses surprise, as Lord Mace is well known to have besieged Storm's End for over a year during Robert's Rebellion. Lady Olenna dismisses her son's role, as "all he laid siege to was the banquet table in the command tent."
Mace presents Joffrey with a magnificent golden chalice with seven facets, one for each of the major houses in the Seven Kingdoms. He encourages his daughter and soon-to-be son-in-law to both "drink deep". Joffrey graciously accepts his gift. He gives away Margaery at the wedding before taking his place in the Great Sept of Baelor. Later on, as the party moves from the Sept to the reception feast outside the Red Keep, Mace tries to attract Tywin's attention, but Olenna quickly waves him away. Some time later, during the wedding feast, Mace is visibly upset by a mock reenactment of the War of the Five Kings in which the dwarf representing Renly Baratheon rides a bare-bottom figure meant to represent Loras.
After Tyrion Lannister is arrested for the assassination of King Joffrey, Lord Mace accepts Tywin's proposal to be one of the judges for Tyrion's forthcoming trial, the other two being Tywin himself and Prince Oberyn Martell.
Mace later attends the coronation of Tommen Baratheon.
Alongside Tywin and Oberyn, Mace sits as a judge during the trial of Tyrion Lannister. He is shocked when he learns that Shae was Tyrion's whore as well as handmaiden to Sansa Stark. The trial is brought to an end when Tyrion demands a trial by combat.
Mace is present during Tyrion's trial by combat and witnesses Oberyn's gruesome death at the hands of Gregor Clegane.
Mace Tyrell is one of the many lords present at Tywin Lannister's wake.
Some time later, Lord Mace attends a meeting of the Small Council. Like Grand Maester Pycelle and Kevan Lannister, he is somewhat disturbed to see that Cersei has appointed Qyburn to replace Varys. He nonetheless hastily puts himself forward as a candidate for Hand of the King, but Cersei declares that he is instead to be jointly appointed Master of Ships and Master of Coin.[
Mace Tyrell is present during the wedding ceremony of Tommen Baratheon and his daughter Margaery. Later, Mace and the rest of the Small Council listen to the High Septon demand the arrest of all members of the Sparrows and execution of the High Sparrow. He is shocked to hear a man who is the head of the Faith of the Seven was visiting a brothel.
In a Small Council meeting Mace reveals that the Iron Bank has called in one tenth of the Crown's debts. When asked by Cersei, Mace admits that the Crown can not pay back more than half of the demanded sum. When Mace offers that House Tyrell could lend the needed money to the Iron Throne, Cersei politely refuses, stating that the Tyrells have already given too much. She then tasks Mace with personally travelling to Braavos to negotiate better terms with the Iron Bank. She also tells Mace that the king, concerned for his father-in-law's safety, has assigned Ser Meryn Trant to escort Mace to Braavos. Mace and Meryn leave immediately, prompting Pycelle to state that the Small Council grows smaller and smaller.
After arriving in Braavos, he is greeted by Tycho Nestoris who welcomes him in the name of the Iron Bank. On the way to the Iron Bank, he talks with Tycho about the harvest in the Reach and King Maegor III who once outlawed moneylending. Unbeknownst to all of them, they are followed by Arya Stark, who recognised Ser Meryn. Arriving at the Iron Bank, Mace admires the facade of the enormous building, stating that the men of the Iron Bank are the world's best gamblers much to Tycho Nestoris' disapproval. After an unspecified time of negotiation, Tycho tries to bid farewell to Mace (whom he clearly dislikes due to his bumbling behaviour), but Mace does not realise this and continues plaguing Tycho on the way to the docks, loudly singing.
At night, while following Trant, Arya overhears Meryn telling two Lannister soldiers how poorly he thinks of Mace and the Tyrells, going as far as calling them traitors.
Mace Tyrell is attending a Small Council meeting that is interrupted by Jamie, Cersei, and Gregor Clegane. When Cersei questions Olenna Tyrell's presence, Mace begins to defend his mother but she quickly speaks for herself. Mace rises and follows his mother and Kevan Lannister when they leave the chamber.
Later, Mace leads Tyrell troops through King's Landing, meeting Jaime Lannister and pausing to give a rather pompous speech. They proceed to the Sept of Baelor to stop Margaery's walk of atonement and free both his children. Lady Olenna also joins them. After Jaime and the High Sparrow square off and Tommen emerges from the sept, Olenna signals Mace to stand down his men. After the King gives a speech, Mace is baffled and asks his mother what's happening. She tells him the High Sparrow has beaten them.
Mace is present when King Tommen makes a royal announcement regarding the date of both Cersei and Loras's trials and that the practice of trial by combat is abolished. Mace is visibly uncomfortable during the king's speech but does not speak.
Mace is present when his son Loras is mutilated by command of the High Sparrow after he is found guilty at his trial. He, Margaery, Loras, and everyone present at the trial die from the explosion of wild fire planted by Cersei in her to plot destroy the High Sparrow and his followers
Lord of Highgarden, Warden of the South, and father to Queen Margaery, Mace Tyrell served as Master of Ships on the Small Council. When Cersei took charge of the Council, she added Master of Coin to his responsabilities and sent Mace to Braavos to renegotiate the kingdom's terms with the Iron Bank. He returned to find Margaery and Loras imprisoned, and worked with the Lannisters to rally Tyrell forces to free them. Along with his children, he was killed when the Sept of Baelor exploded.