House of the Dragon season 3 trailer cleverly sets-up a major tragedy to come from George R.R. Martin's book

The latest trailer for House of the Dragon season 3 is full of battles and bloodshed, but there's one blink-and-you'll-miss-it moment that sets up a major tragedy to come from George R.R. Martin's Fire and Blood book.

A warning that the following will contain major spoilers for the House of the Dragon source material, including events that will likely be adapted for season 3 and beyond. Turn back now if you don't want to know what happens next!

Season 3 is set to open with the Battle of the Gullet, a naval clash that, tragically, sees the death of Jacaerys Velaryon, who is Rhaenyra's heir.

In the trailer, a voiceover from Daemon is heard saying "You will have an empire unassailable, Rhaenyra, and our children will rule it forever and a day." Right after this line, we see Jacaerys standing behind Rhaenyra.

"The camera focus shifts to Jacaerys, who was meant to be the next monarch, then cuts to him flying off to his death, for those very children to eventually take the throne," one fan on Twitter points out. In Fire and Blood, Rhaenyra's sons with Daemon, Aegon and Viserys, are sent to be fostered in Pentos, and the Triarchy (allied with the greens) take them captive on the way. Aegon is able to escape on his dragon and flies to Dragonstone to warn the blacks. This sparks the Battle of the Gullet.

In the battle, Jacaerys's dragon Vermax is wounded and sent sinking into the ocean, and, while Jace is able to escape drowning, he is swiftly killed by crossbow fire.

After Jacaerys dies, Rhaenyra's next son Joffrey Velaryon becomes heir – though, in Fire and Blood, Joffrey is also ultimately killed. That leaves Rhaenyra's firstborn son with Daemon, Aegon, as heir to the Iron Throne. Aegon does indeed eventually become king, and it is from him that the Targaryen line we know from Game of Thrones is descended. So, Daemon was tragically right that it is his and Rhaenyra's children who will rule their empire, though he was likely referring to Jacaerys and his betrothed Baela (Daemon's daughter).

With the Battle of the Gullet set to come early in the season, that means we'll be losing Jace early, too, which will surely affect the plan Rhaenyra and Alicent devised for the greens to surrender in the House of the Dragon season 2 ending. What happens next remains to be seen, but, judging by the trailer, it won't be easy going for team black or team green as the Dance of the Dragons gets more intense.

House of the Dragon returns this June 21 in the US and June 22 in the UK. In the meantime, check out our guide to all the most exciting upcoming TV shows to fill out your watchlist.