

The name Ninepenny came because of a comment from Prince Duncan Targaryen, who said “ Crowns were being sold for nine a penny,” pointing at the fact that there were nine different claims to the throne at the moment.

The War of the Ninepenny Kings (also known as the Fifth Blackfyre Rebellion) was a war among many of the Free Cities, started by the Band of Nine. You can check out the narrative in the video clip below, uploaded by Elio García, the co-author of The World of Ice and Fire :

For those of you who have forgotten, Brother Ray, portrayed by Ian McShane, was a character in Season 6 of Game of Thrones, who saved The Hound – Sandor Clegane, and was later brutally murdered by some members of the Brotherhood without Banners who were then brutally murdered by Sandor Clegane.
