Ghazghkull Mag Uruk Thraka

"'Oi! I got a joke for you. Whatdya call a cheap tooth-removal? A RIP-OFF!'"Ghazghkull Mag Uruk Thraka is the leader of the Goffs clan, and the Warboss with the single largest army of Orks in modern history.

Official Canon
Ghazghkull had been an ordinary Ork until he started receiving visions from Gork & Mork that he would lead the greatest Ork horde to conquer the galaxy. Ghazghkull started winning battles and gaining forces until WAAAGH! Ghazghkull became the largest Ork WAAAGH! since the War of the Beast.

Twice, Ghazghkull attacked the planet Armageddon, an important industrial world, and secretly the planet Ullanor, the capital of the old Ork empire. While these massive battles caused much havoc, they failed to take the planet. He is currently a journey to start Rangok, the Greatest WAAAGH! that will ever exsit

TTS Canon
Ghazghkull has arrived at the Ork empire of Octarius to secure the empire's forces as his own after defeating its overfiend, Blaktoof. He spared Blaktoof to enlighten him about the word of Gork & Mork.

Trivia

 * Alfabusa noted that Thraka’s appearance is far too early in the story, as he intended to give him more set-up before he became relevant to the main plot.