the world is plunged into darkness
A literary, somewhat archaic expression describing a state where heaven and earth are dark, often used figuratively for a world without light or hope. Rare in modern conversation.
Heaven and earth are in darkness; not a single ray of light can be seen.
A Sino-Japanese compound from 天地 (heaven and earth) and 晦冥 (darkness, obscurity). The exact historical derivation is uncertain; it is a literary set phrase.