Domdaniel is a fictional cavernous hall at the bottom of the ocean where evil magicians, spirits, and gnomes meet.
It had been prophesied that the spirits of the Domdaniel were destined to be destroyed by a member of that family, so they sought to put an end to it.
But the youth Thalaba accomplishes the destruction of the magicians in the final volume of the poem despite their efforts to kill him and his surviving family.
In T.H White's book The Sword in the Stone Merlin, before his famous duel of magic with the witch Madam Mim, says: "Now we shall see how a double first at Dom-Daniel avails against the private tuition of my master Bleise".
Domdaniel is the headquarters of the Spanish Inquisition in Neil Gaiman's graphic novel Marvel 1602 and includes large caverns.