*phlegethon*

‖n. [ L., fr. Gr. &unr_;, prop. p. pr. of &unr_; to blaze. ] (Class Myth.) One of the principal rivers of Hades, in the channel of which fire flowed instead of water.

Fierce Phlegethon,
Whose waves of torrent fire inflame with rage. Milton. [ Webster 1913 Suppl. ]