Oberyn Martell

Oberyn Martell is character that will debut in the the fourth season. . He's a member of House Martell

Prince Oberyn, known as the Red Viper of Dorne, is the younger brother of Doran Martell, the Prince of Dorne, and the older brother of the late Elia Martell.

In the books
In the A Song of Ice and Fire novels, Prince Oberyn is hot-headed younger brother of Prince Doran Martell. He has eight bastard daughters, called the Sand Snakes, the four youngest of which by his current paramour, Ellaria Sand.

Oberyn has a lined face with thin eyebrows, black "viper" eyes and a sharp nose. His hair is lustrous and black with only a few silver streaks and recedes from his brow into a widow's peak