Oneiroi is the general term for inhabitants of Nightmare.
First there is Grimm, the Hunger Wolf, the eldest, who rules over Nivose, called also the Empty Quarter. His subjects are called morauxe. Singular moreau. His citadel is the Bone Fortress.
Second is Nox, Regent of Air and Darkness, whose domain is Brumaire, the Void. Its people are the djinn.
Third and Fourth are the twins, Agni, the Fire Witch, and Chuzz, the Sea Witch, who rule Thermidor and Pluviose, and who share the title of Lords of Chaos. Inhabitants of Thermidor are aefrits, inhabitants of Pluviose are called undines.
Fifth is Fellmonger, who rules over Messidor, and is Lord of the Dreams of the Dying and who eases their passage, and who has taken the Daughters of Death, the Plague Sisters, to be his queens. The Fellmonger's subjects are the norns.
Sixth is Heget, called the Voluptuous and the Deceiver, whose domain is Verdemaire, the Garden of Heart's Desire. Her people are called incubi and succubi.
Seventh is Chimiculeon, the Armored King, who is lord of Ventose, which births the creeping ones, called also the chigoes. His citadel is called the Malignium.
Eighth is Xor the Silent, master of Ferose, whose subjects are built, not born. Its people are the forged.
Ninth, there is Mistigris, the Patterned Jester, the Gambler, whose kingdom is Bascose, the Land of Uncertainty. His/her subjects are the rashlings.