When Rhaenyra holds the Valyrian steel dagger in fire, inscribed words are revealed: "From my blood come the Prince That Was Promised, and his will be the song of ice and fire"; these are almost the same words Rhaegar Targaryen said about his son Aegon in a vision Daenerys saw at the House of the Undying (A Clash of Kings, chapter 48): "He is the Prince That Was Promised, and his is the song of ice and fire".
The episode title refers to a title used by claimants to the Stepstones in the southern narrow sea. The first person to style himself the title was Daemon Targaryen. In the novels, the full title is "King of the Stepstones and the Narrow Sea".
Milly Alcock told the New York Post that when filming the brothel orgy scene in this episode, director Clare Kilner made sure that she and Matt Smith hadn't seen any of the extras until they were shooting. She said it was quite shocking and "kind of weird and silly" as they made their way through the naked bodies. She said, "There were extras who we had just met who were like, 69-ing for 12 hours. It's pretty gnarly. We felt pretty overdressed, because everyone else was nude."
The parade of suitors for Rhaenyra takes place at Storm's End, the seat of House Baratheon. This episode marks the first time we see the castle, on either Game of Thrones (2011) or this show. There had been plans to feature the castle in the background during the parley between Stannis and Renly Baratheon in Garden of Bones (2012), but the budget wouldn't allow it.
In the episode we see Lucas Blackwood and a boy from House Bracken argue and then fight (until they kill each other). In the books by George R.R. Martin, the classic feud between the Brackens and the Blackwoods is often mentioned. If a lord of one of the families chooses one side, the lord of the other family chooses the other side just out of spite. In the series itself, in the future, the two houses will fight on opposite sides of the Targaryen civil war: the Blackwoods with the Blacks of Rhaenyra and the Brackens with the Greens of Aegon II and Alicent.