Thiassi the Lightning Bringer

Thiassi the Lightning Bringer is the brother of the king of storm giants, Gymer. After his conversion into an undead flesh giant, he lured his brother into a trap.

Antiok, grand necrolord of the Scourge, rides upon his shoulder.

Trivia
His name is obvious reference to Thiassi, giant from Norse mythology who tried to trick gods by stealing their apples of youth. He was killed and Odin threw his eyes to sky, where they became stars.