Mace Tyrell
Lord of Highgarden and Warden of the South, a genial, self-important man who commands the realm's richest lands and does mostly what his mother tells him.
The fuller tale
Mace Tyrell holds the titles of the realm's second-richest house — Lord of Highgarden, Defender of the Marches, Warden of the South — and the tale's running joke is the daylight between the offices and the man. He is genial, vain, expansively self-satisfied, and the last person in any room to understand what just happened in it; his mother supplies the strategy, his children supply the charm, and Mace supplies the signature and a certain unkillable enthusiasm. The books give the joke its founding text: his one command in Robert's Rebellion was besieging Storm's End, which he conducted by feasting within sight of the starving garrison for a year, and his one battlefield laurel, at Ashford, was won by his subordinate Randyll Tarly before Mace arrived.
And yet — the story is careful with this — the house he fronts keeps winning. The Tyrell playbook of the middle seasons runs through Mace's nominal authority: the pivot from Renly's corpse to the Lannister alliance, the Blackwater relief, the weddings that put his daughter beside two kings in succession. He serves on the small council as master of coin and does the job the way he does everything, loudly and adequately, while the real Tyrell business is transacted over his head by his mother and under it by his daughter. Power, the tale keeps observing, sometimes wears a man the way a man wears a hat.
His redeeming feature is entirely sincere: Mace loves his children. When the Faith takes Margaery and Loras, the bluster drops away and something almost formidable stirs — he marches his strength into King's Landing in the show and storms the sept steps demanding his daughter, and the books leave him at the head of a Tyrell army camped around the capital with his patience running visibly out. The fool of the small council, both tellings agree, is dangerous in exactly one direction.
The page and the screen
Book Mace is less buffoon and more blowhard-with-leverage: the books keep him permanently camped between the reader and the throne — angling for the Handship, promoting his cronies, besieging Storm's End again — and the realm's regents fear his army even while the story mocks his judgment. His Ashford 'victory' and the year of feasting outside Storm's End are book details the show never states. The show, needing a comic register for the Tyrell scenes, pushed him further toward farce — the Braavos singing, the wardrobe — and then gave him an ending; in the published books Mace is alive outside King's Landing with the Reach's power at his back and both his children in the Faith's hands, a situation with considerably more gunpowder in it than his show fate allowed.
Where they stand, season by season
Their fate — if death has found them, it is written here. Open at your peril.
The show: Died when the sept burned (S6·E10)
The amiable Lord of Highgarden followed his children into the Great Sept for Loras's trial and died with them in Cersei's green fire, the last Lord Tyrell of the old line.
In the show he dies as he lived: adjacent to the point. Summoned to the Great Sept of Baelor for Loras's trial before the Faith, Mace stands in the crowd as his son confesses and is mutilated, visibly grasping, one beat behind everyone, that something is wrong — Margaery has read Cersei's absence correctly and is trying to empty the building. The High Sparrow's certainty holds the doors, and the wildfire cached beneath the sept takes the congregation whole: Mace, his daughter, his son, the Faith's leadership, and the future of House Tyrell in a single green bloom over the city. He is alive in the published books, at the head of an army, with no idea what the show has planned for the ground beneath the sept.