Emilia Clarke - who played Daenerys Targaryen in all eight series of the HBO fantasy epic - threw herself into the role and was even able to write her own Valyrian monologue in which her character ordered the execution of one of three Meereenese noblemen suspected of conspiring against her.
Discussing the speech - which was in English for the original script - in an outtake for James Hibberd's book Fire Cannot Kill a Dragon, director Jeremy Podeswa said: "There's usually a lot of preparation for that sort of thing and so much consideration that goes into it and she had quite a big monologue before she sets the guy on fire.
"I went over to Emilia and I was like, 'I know this is a really big ask, but do you think you could figure out a way to do this in Valyrian?' She said, 'Yeah, sure, I think I can do this.'
"And I'm all, 'Really?' Then she went off and cobbled together things that [Daenerys] had said in the past that made sense. She came back in 10 minutes and had this whole monologue down."
Typically, the fictional language was scripted months in advance for filming, but Emilia, 34, was able to improvise for the scene in season five after her experiences on the show up to that point.
Jeremy added: "I just had to hand it to Emilia for taking on the challenge and making it completely credible.
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"Every single take, every intonation, and the way she phrased everything, you completely understood what she was meant to be saying. Then the subtitles all seemed authentic to what she was doing.
"She knew the language well enough at that point to make it all work. It wasn't tracking perfectly in Valyrian, but no fan ever noticed it. She did an amazing job."
