"Game of Thrones" season 4 cast is ever expanding, with the latest being Michiel Huisman joining the HBO series in a yet unnamed role.

First reported by The Hollywood Reporter, Michiel Huisman ("Nashville," "Treme") will join the cast in some capacity, after Huisman's trainer posted an Instagram photo showing the acting bulking up for season 4.

Currently, "Game of Thrones" season 4 is filming its expansive season, and the cast is ever growing.

In addition to Huisman, actor Joseph Gatt has joined the "Game of Thrones" season 4 cast, presumably in the role of Styr, Magnar of Thenn. However, "Game of Thrones" has a habit of keeping its cast roles under wraps.

But a few cast members are joining with already announced roles as well, including Roger Ashton-Griffiths as Mace Tyrell. He will likely shares lots of screentime with Natalie Dormer and Dame Diana Rigg, who plays Margaery Tyrell and Lady Olenna, respectively.

Indira Varma ("Luther") will also grace "Game of Thrones" season 4 in the role of Ellaria Sand, the lover of Prince Oberyn Martell in the books.

And the two biggest casting news for "Game of Thrones" season 4 so far is Mark Gatiss and Pedro Pascal.

Mark Gatiss is already finished filming for season 4, but his role remains a mystery. "Sherlock" fans will know him as Mycroft.

Pascal will join Indira Varma as Oberyn Martell aka The Red Viper.