Nightmare of Dominus Ghaul
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The Nightmare of Dominus Ghaul is a Nightmare of Ghaul that appears in Shadowkeep. Like all Nightmares, it is a manifestation of the Guardian's fears and trauma generated by the Darkness, and is used by the Darkness to taunt the Guardian by reminding them how easily the Light was taken from them.
The Guardians would confront the Nightmare of Dominus Ghaul after they managed to enter the Pyramid, forcing them to fight the Nightmare is a similar manner to how they fought the original Ghaul. Fortunately, the Guardian persevered against the Nightmare of the Dominus, allowing them to gain deeper access into the Pyramid.
After their journey into the Pyramid, the structures energies continue to seep into the Solar System causing some of the stronger Nightmares to return. Among them, the Nightmare of Dominus Ghaul would return, representing the Essence of Rage. The Guardians would then conduct Nightmare Hunts to keep the Nightmares at bay.