As backwards as many of the habits practiced in Westeros are - we've seen enough of House Bolton's love of flaying, for starters - human sacrifice is the reserve of Melisandre, the priestess of R'hllor who has stood by Stannis Baratheon's side in his quest for the Iron Throne. It's been a while since she burned anyone alive as an offering to the one true god (Stannis burned Mance Rayder at the stake, but that was for treason not to appease the Lord of Light), but there were plenty of hints that the next victim of this awful practice would be Stannis' own daughter Shireen, disfigured by greyscale but nevertheless carrying king's blood in her veins. The moment Stannis ordered Davos Seaworth back to Castle Black it became clear that he was going to do the unthinkable. Led to the pyre, Shireen could do nothing to prevent her fiery sacrifice, her high-pitched screaming getting under the audience's skin as Stannis watched on.
