noun, adverb
a long time ago; in those days; once upon a time
Archaic literary expression for 'long ago' or 'in ancient times'. Modern Japanese typically uses その昔 or 昔.
See also: その昔 (そのむかし)
その上、この地には大きな都があったという。
Long ago, it is said there was a great capital in this land.
その上の物語を語り継
They pass down tales from those ancient days.