Lord Ghûlmagak

Ghûlmagak is an ancient Chaos Lord, from the time before the Empire was formed.

In the mission Festering Ground, the Heroes goal is essentially to bury the Monolith of Ghûlmagak. Later, in The War Camp Mission, Bödvarr Ribspreader references this by hinting that the Heroes destroyed Ghûlmagak's artifacts and killed Chaos Warriors.

Trivia
Lord Ghulmagak was created for the Vermintide 2 game and never mentioned before in the Warhammer Fantasy lore.