Underworld river WSJ Crossword Clue

Think of a place where the living rarely tread, and a name that might sound like a rock band.

???? is a river in Greek mythology that forms the boundary between Earth and the Underworld.

The clue refers to Greek mythology, where the River ???? is one of the rivers in the underworld, Hades. It is often depicted as a boundary between Earth and the Underworld, where souls are ferried across by Charon.

"Dread river of oath," per Homer, River of the Greek underworld, Where Achilles took a dip, River of the Greek underworld, River that Milton called “the flood of deadly hate”