Nightmare of Dominus Ghaul

"The Red War saw so many lives lost. Saw the Light taken away so easily. In Light, there is only weakness."

- The Darkness to the Guardian, upon banishing the Nightmare of Ghaul

The Nightmare of Dominus Ghaul is the Nightmare of the late Dominus of the Red Legion: Ghaul. It serves as a manifestation of the Guardian's fears and trauma—created by the Lunar Pyramid—and is used to taunt them by reminding them of how easily the Light was taken from them. Years later, it would reemerge aboard the Derelict Leviathan to torment Empress Caiatl, who would descend into the Underbelly of the vessel in an attempt to confront it.

Shadowkeep
The Nightmare of Dominus Ghaul's appearance in Shadowkeep appears to have served as merely a functionary, as it does not speak or otherwise socially interact with the Guardian. It exists only as an obstacle to progression, whether that was entrance to the Lunar Pyramid, or as the focus of a Nightmare Hunt instructed by Eris Morn.

Season of the Haunted
In Season of the Haunted, the Nightmare of Dominus Ghaul takes on a speaking role, taunting Empress Caiatl over the current situation of the Cabal. As a beacon of the martial might of the Cabal, the Nightmare continually pressed Caiatl on her actions since his death, such as fleeing Torobatl, allying with the Guardians (which it sees as subservience), and more. It professed a strong belief that everything Ghaul had done to shape Caiatl as a warrior had gone to waste, with Caiatl struggling to surpass this opinion. Eventually, Caiatl looks past the domineering and suicidal course that the Nightmare contends the Cabal should continue upon, and transforms the Nightmare of Dominus Ghaul into a Memory of Dominus Ghaul. Thus, everything it stands for became a reminder of how the Cabal shouldn't act in the future of its civilization.

List of appearances

 * Destiny 2
 * Shadowkeep
 * Season of the Haunted