I haven't read the books but, based on the other stuff I've rerad, there are some significant differences. One that I found interesting is that Jon Snow fought the Thenn's when Bran was in the tower, not Tormund's group. Another is that Theon didn't have that iron born guy whispering in his ear, it was a captured Ramsay Snow acting like Reek, his late servant (who he is brain washing Theon to believe he is, as a replacement for his fallen nigguh).
...
I may have got sucked into a spoiler blackhole on ASOIAF wiki last night.
Also, am I the only one who found the Thenns to be badass? I know they eat people and shit, but I wanna see them in battle. The leader had this very "I don't give a fuck, I will kill you all"-esq attitude in his body language. Great acting imo.
that iron born guy is ramsay
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