Through fire and blood House of the Dragon has roared back onto HBO for Season 3, and if you've watched episode 1, you might need a cup of tea.

In a colossal, jaw-dropping episode involving the much-anticipated Battle of the Gullet and many deaths, events conspired that will change everything for Queen Rhaenyra (Emma D'Arcy) and her son, Jacaerys Velaryon (Harry Collett). And Mashable asked the cast about it, so consider this a major spoiler warning.

What happens in House of the Dragon Season 3, episode 1?

In Season 3, episode 1, we're finally here: the Battle of the Gullet, an inevitability the show's been foreshadowing for two seasons with Lord Corlys Velaryon's (Steve Toussaint) all-important blockade. When the Triarchy shows up, led by Admiral Sharako Lohar (Abigail Thorne), the battle finally begins.

However, on Dragonstone, Rhaenyra finds herself barred from flying into war by one more man standing in her way, one she didn't expect: her son, Jacaerys. Locked in her chambers by her Queensguard, wearing her riding leathers, Rhaenyra is frustrated enough to tear her court dress to shreds. But it's complicated.

"For two seasons we've seen Rhaenyra restrained from action, often by her male council," D'Arcy tells Mashable. "And at the start of Season 3, there's finally huge momentum in her campaign, and she is poised to move into action. That momentum hits a very sudden brick wall — or locked door.

"Rhaenyra has become very familiar with the ways in which patriarchy looks to consolidate male power, and there's something interesting going on here, where something that's framed as protection or care is actually an arm of control. I think that's a strong tool within the toolkit of patriarchy."

Why did Jace defy Rhaenyra?

For Collett, Jace's decision to defy his mother and fight in the Battle of the Gullet in her stead isn't one of malevolence (though it's technically treason). We watch Jace pitch the move as one of valor to his fiancée Baela Targaryen (Bethany Antonia), as a means to prove his worth as the future king of Westeros.

"There's no malice behind it. If she goes, then she could die, and I feel like he'd rather die than lose his mother. It's a protective thing," Collett tells Mashable.

"If things did go his way, then he would have locked her up, won the battle, come back, dealt with the consequences easy, but he still would have won the battle. Well, he technically did win the battle anyway, but he lost his life in it. But there's nothing malicious about it, just all protective."

Fans are processing the loss of Jacerys and his dragon Vermax, brought down in the midst of battle despite the efforts of Baela and her dragon Moondancer. They're left floating in the turbulent waters between Dragonstone and Driftmark. It's a shocking, deeply upsetting moment, watching Vermax thrashing to survive, slowly going under, with Jace plunged into open water. Then, Triarchy arrows end the young prince's life.

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Collett took us through how the House of the Dragon team helped him prepare for Jace's tragic demise, ranging from horse riding lessons and wetsuit fittings to developing techniques for conveying emotion on a dragon rig.

"I had loads of meetings with Loni [Peristere], the director of the episode, and Ryan [Condal] talking about how I can portray feelings while being up in the air and having all this stuff going on around me," he said. "We would make up scenarios that would happen with Jace that didn't happen in the show, which really helped me get into character...It was really fun this time around, because I finally get to get out the offices."

When asked about what he learned this season about riding dragons, Collett had one response.

"God, don't fly low next time."

So, what's next for House of the Dragon after Jace's death?

Here's a few things to think about:

• Jace was the only one who saw Sheepstealer's rider, Rhaena Targaryen (Phoebe Campbell), who has now fled.

• Rhaenyra doesn't know another of her sons is dead and that she's one major dragon down, so she's likely to react.

• The young Joffrey Velaryon is Rhaenyra's sole blood heir now, but he's in the Vale, under the protection of Lady Jeyne Arryn (Amanda Collin).

• Baela was betrothed to Jace but she's still a high-ranking member of the house, being Daemon Targaryen's (Matt Smith) daughter.

• We still don't know whether or not Corlys is alive.

• Harry Collett was not slain in battle as Jace. He's an actor and totally OK.

House of the Dragon Season 3 premieres June 21 at 9 p.m. ET on HBO and HBO Max, with a new episode every Sunday.