While most of the walking scenes beyond the Wall were filmed in Iceland, the frozen lake sequence was filmed in the Wolf Hill rock quarry near Belfast, Northern Ireland. The set was completely paved with concrete to serve as the ice, dressed with (plaster) rocks, and then covered in fake snow. About a 1000 links were made and painted to create 400 feet of rusted chain. According to the crew, the actual temperature was so cold that the actors did not have to act as if they were freezing.
In Kissed by Fire (2013), Beric Dondarrion smeared his blood on his sword to make it flame. According to Richard Dormer, Beric and Thoros of Myr originally needed to use their blood and recite a short prayer for this feat of magic, but over time, they have gotten so skilled that they can light the sword without blood while only thinking the words. On set, the fire swords were real props that had to be refueled every two minutes. In the novels, they use wildfire to make their swords burn, but this also gradually wrecks the steel.
This marks the first appearance of a wight polar bear after the introduction of wight horses and wight Giants, which suggests that the White Walkers can resurrect every dead animal. The writers of the show had written the bear in for the last four seasons, but had to be told by the special effects team each time that they could not afford one. In the novels, an encounter with one already happened at a much earlier point, during the battle of the Fist of the First Men; one of the Night's Watch members nearly cuts the creature's head off, but it is still able to decapitate the man with one swipe of its paw.
This episode was accidentally aired by HBO Spain 5 days before its official release.
Upon airing, this was the longest episode of the series, with a runtime of 71 minutes, surpassing the 69 minute run time of The Winds of Winter (2016), although HBO had previously announced that the following episode, The Dragon and the Wolf (2017), would break this record by ten minutes.