There's a bit of a cold war going on in House of the Dragon season 3. Rhaenyra Targaryen (Emma D'Arcy) has finally claimed the Iron Throne, and she now gets to rule over King's Landing with six dragons of fighting age right by her side. On the other side of the coin, Ormund Hightower (James Norton) has taken over Tumbleton, from which he works tirelessly to overtake the crown and make his ward, Daeron Targaryen (Benjamin Evan Ainsworth), rule over the Seven Kingdoms.
This is a tricky situation for both parties. Rhaenyra can't simply send a dragon to burn Tumbleton as a whole—which houses Ormund's men—because the city swore loyalty to the queen and is filled with countless innocent civilians. Ormund, however, can't attack Rhaenyra directly because Daeron is the only one with a dragon of fighting age, and he would quickly be overpowered. As such, the two have found themselves in a stalemate... but that hasn't stopped either party from making moves outside the board.
During the final moments of House of the Dragon season 3 episode 6, audiences witness Corlys Velaryon (Steve Toussaint) being attacked. All the while, Rhaenyra is handed a piece of cloth with a message written in blood. So what exactly happens, and how does it all tie in with the assassination attempt on Daeron Targaryen?

Rhaenyra is handed the vest of one of the Baratheon men she sent to kill Daeron Targaryen
During the first half of House of the Dragon season 3 episode 6, we see a delegation from House Baratheon arrive at the Red Keep. Lord Borros Baratheon (who appeared during the season 1 finale moments before Lucerys Velaryon's death) doesn’t arrive in person, which visibly displeases Rhaenyra. Still, the Queen manages to find a use for the men who arrived at her doorstep.
Since almost no one knows about the whereabouts of Aegon (Tom Glynn-Carney) and Aemond Targaryen (Ewan Mitchell), Daeron is the biggest threat to the crown. After all, he's the youngest son of former King Viserys Targaryen (Paddy Considine). As such, Rhaenyra sets out to "eliminate the competition" and sends the Baratheon delegation straight to kill Ormund and Daeron.
The Baratheon men do as they are ordered, and they soon arrive at Tumbleton. In order to be granted passage into the city, they claim that they have arrived to swear their loyalty to the “new king,” Daeron Targaryen (although this is just a big ruse). Unsuspecting of their true intentions, Ormund lets them into his quarters, and everything would go according to plan if it isn’t for one unforeseen guest: Ser Gwayne Hightower (Freddie Fox).
Gwayne was supposed to be fighting Rhaenyra's land army, but he deserted after realizing that it was nothing but a suicide mission. He then returned to Tumbleton and is present when the Baratheon men attempt to assassinate Daeron. Gwayne quickly notices that something about the delegation is off. As such, he fights and kills these soldiers before the Greens are left without yet another one of their members.

In retaliation for Rhaenyra's attack, Ormund grabs the vest of one of the Baratheon men and writes a haunting message on it with blood: "Kick this dog and it will bite your hand." He sends this "gift" to Rhaenyra, and also sends some members of his army to capture Corlys and his men—which is a very clever and strategic move. After all, Ormund knows that the Velaryon army was supposed to reinforce King's Landing now that the city is living through some dark days.
When Queen Rhaenyra hears petitions from the smallfolk earlier in the episode, the delicate matter of the city's protection is raised. Members of the City Watch of King's Landing have slowly but steadily been killed by Ormund's assassins hiding in the city. Those who remained alive have resigned from their posts, as not only were they at risk of losing their lives, but the crown hadn't been able to pay them, either. As a result, Rhaenyra publicly announces that she would ask for men from the Velaryon army to protect the city in the meantime.
Ormund is seeking retaliation for the assassination attempt on Daeron, and since he knows about Rhaenyra's plans, he is able to act in advance and kill members of House Velaryon. For the time being, it seems the Greens are two steps ahead, and it will be interesting to see how the Blacks fight back.
New episodes of House of the Dragon season 3 air every Sunday on HBO and HBO Max.
