'Game of Thrones': The real history behind 'Red Wedding' massacre

"The Lannisters send their regards."

There's a lot of Game of Thrones that's pure fantasy, such as dragons, three-eyed ravens, giants and those creepy old White Walkers. Yet George RR Martin has also worked some real stuff into the sprawling adventure and drama of his books and HBO TV series, including his infamous "Red Wedding" massacre.

Out Tuesday on Blu-ray and DVD, Game of Thrones: The Complete Fifth Season lets fans catch up before new episodes begin April 24 and also features a special collection of bonus material that offers Martin and historians explaining how history has factored into Westeros mythology from the beginning.

This exclusive clip discusses the ninth episode from the third season — titled "The Rains of Castamere" — where the wedding of Edmure Tully (Tobias Menzies) and Roslin Frey (Alexandra Dowling) goes south when Walder Frey (David Bradley), the host of the occasion, perpetrates the murder of King Robb Stark (Richard Madden), his family and his men during the reception.

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For inspiration, Martin pulled from two incidents that occurred in Scotland centuries ago: "The Black Dinner" of 1440, where a dispute with 10-year-old King James II led to the deaths of two important members of the powerful Clan Douglas, and the 1692 Glencoe massacre, where guests of the MacDonald clan slaughtered 38 of their hosts — though with the "Red Wedding," Martin admits he reversed that.

Adds the writer: "Scottish history is an amazing source for all of this because it's one of the most incredibly bloody histories of any country that I've ever studied."