Quartus

Quartus was one of the seven princes of Stormhold, and the fourth son of the King of Stormhold.

Book
Quartus is one of the dead sons of the King of Stormhold. He was killed by either Primus or Tertius, although it is not clear how he was murdered.

Movie
Ten years prior to the events of the film, Quartus was murdered by his elder brother Secundus. Secundus told his brother he had a sore foot, and requested Quartus fetch him ice for it. Quartus obliged, and Secundus locked him in the cold store; causing him to freeze to death. His body is covered with a thin layer of frost. He is sarcastic in a way but serious depending on the situation. When Secundus was murdered by his brother Septimus - with aid from his father - at their father's deathbed, Quartus took the opportunity to taunt his dead brother. Once Tristan Thorne became the next King of Stormhold, Quartus passed on to the afterlife with his brothers.