Complex sentence: In 2015 he will join the cast of the HBO series Game of Thrones in Season 5 as Keyr; an expanded role from the unnamed slave he previously portrayed in Season 4.
Split into simpler sentences: In 2015 he will join the cast of the HBO series Game of Thrones in Season 5 as Keyr. This is an expanded role from the unnamed slave he previously portrayed in Season 4.