The six sisters are six huge trebuchets built by the forces of Yunkai for the Second Siege of Meereen.
The trebuchets tower forty feet high above the tents of the Yunkai'i and are the Yunkish siege camp's chief landmarks. They are arrayed on three sides of the city, all but the Skahazadhan riverside, and are surrounded by piles of broken stone and casks of pitch resin just waiting for a torch. They are named:
- Ghost of Astapor
- Harpy's Daughter
- Harridan, the largest of the trebuchets
- Mazdhan's Fist
- Wicked Sister
A Dance with Dragons
The Yunkai'i ships bring lumber and hides up from the south, enough to raise six huge trebuchets outside of the city of Meereen. As Queen Daenerys Targaryen's foes gather all about her she can hear the hammers ringing through the warm, dry air.
The enslaved Tyrion Lannister looks upon trebuchets after being purchased in the auction block outside of Meereen. One of the soldiers walking along beside Tyrion’s cart proudly tells him the name of each trebuchet. According to the soldier just the sight of them drove Daenerys Targaryen to her knees and there she will stay sucking Hizdahr zo Loraq’s noble cock, else the Yunkai'i will smash her walls to rubble.
Bloodbeard suggests using the trebuchets to send Meereenese hostages back to Daenerys.
After Daenerys's disappearance from Daznak's Pit, while the Queen's Hand Ser Barristan Selmy is meeting with the Green Grace, Skahaz mo Kandaq bursts in to tell them that the six trebuchets have begun flinging not rocks, but corpses into Meereen.
The Winds of Winter
In the camp of the Second Sons three hundred yards from where Tyrion Lannister stands rises the Wicked Sister, her long arm swinging up with a clutch of corpses. The dragon Viserion catches one burning body just as it began to fall, crunching it between his jaws.
During the meeting in Ben Plumm's tent Ben informs his men that they have been commanded to defend the Wicked Sister by Malazza, the Girl General. As Ser Barristan Selmy is making for the Harridan, Malazza is afraid he will turn toward the Wicked Sister next.
By this point the trebuchet the Ghost of Astapor is already down. The Mother's Men break the Long Lances like a rotten stick and drag the trebuchet over with chains. According to Ben, Malazza figures Selmy means to bring down all the trebuchets. Jorah Mormont replies he would have done it sooner.
Three hundred yards away the Wicked Sister swung her arm, chunk-THUMP, and six fresh corpses went dancing through the sky. Up they rose, and up, and up. Then two burst into flame.—thoughts of Tyrion Lannister
Crossbows is how you hold the Wicked Sister. Scorpions. Mangonels. That's what's needed. You do not use mounted men to defend a fixed position.—Inkpots to the Second Sons
- ↑ A Dance with Dragons, Chapter 43, Daenerys VII.
- ↑ A Dance with Dragons, Chapter 47, Tyrion X.
- ↑ A Dance with Dragons, Chapter 57, Tyrion XI.
- ↑ A Dance with Dragons, Chapter 70, The Queen's Hand.
- ↑ 5.0 5.1 5.2 Tyrion II (The Winds of Winter)