Icelandic ambient musicians Sigur Rós have joined the cast of the hit HBO series “Game of Thrones” for its upcoming fourth season.

According to Entertainment Weekly, Sigur Rós members Jón Þór “Jónsi” Birgisson, Georg Hólm and Orri Páll Dýrason are currently shooting scenes for “Game of Thrones” season 4 in Croatia, where the show typically shoots scenes set in Kings Landing. There’s no word yet on who the Sigur Rós members will play, but common sense has them pegged as musicians of some kind.

This is not the first time that well-established musicians have made appearances on “Game of Thrones.” In seasons past, The National and The Hold Steady were hired to compose songs based on George R.R. Martin’s lyrics in “A Song of Ice and Fire,” and band members from Coldplay and Snow Patrol have shown up as extras in past episodes. Most notably, Coldplay drummer Will Champion appeared as a drummer/assassin at the Red Wedding and was later murdered by Arya Stark in the next episode.

In another bit of “Game of Thrones” casting news, the show’s producers have once again recast Gregor “The Mountain” Clegane, best known as the murderous brother of fan-favorite character Sandor “The Hound” Clegane. As the LA Times reports, Icelandic actor and strongman Hafþór Júlíus Björnsson will now portray the Mountain, so named because of his freakishly large stature. At 6’9” and 419 pounds, Björnsson should have no trouble filling out the character.

Back in season 1, the Mountain was portrayed by Conan Stevens during a brutal fight with his brother, and when Stevens left the show to work on “The Hobbit” film, the Mountain was portrayed by Ian Whyte for a small appearance in season 2. The character did not appear in season 3.

“Sherlock” co-creator and co-star Mark Gatiss has also signed on to play an unknown character in the fourth season as well. Fansite Winter is Coming claims that Gatiss has been cast as Tycho Nestoris, a representative of the Iron Bank of Braavos who is known for relentlessly pursuing debtors who refuse to pay. Oftentimes, those who refuse to pay back their debts find the Iron Bank funding their enemies. Nestoris doesn’t come into play until later into the books, but seeing as King Joffrey and the Iron Throne are heavily indebted to the Iron Bank, there’s plenty of reason to introduce him early.