Answer: styx

AnswerCrossword Clue
STYXRunner down under?
STYXNetherworld river
STYXRiver encircling Hades
STYX"Divine Comedy" river
STYXEarth-Hades boundary, in Greek myth
STYXUnderworld ferryman's post
STYXNetherworld flower
STYXRiver crossed by Orpheus
STYXSite of Charon's ferry
STYXCharon's waterway
STYXFinal crossing?
STYX"Show Me the Way" rock group
STYX"Paradise Lost" river
STYXRiver down under?
STYXRiver to the underworld
STYXWhere the last ferry leaves
STYXOne hell of a river?
STYXRiver in which Achilles was dipped
STYXRiver of the underworld
STYX"Show Me the Way" band
STYXMoon of Pluto discovered in 2012
STYXRiver of Hate, in myth
STYXCharon's crossing
STYXUnderworld river
STYX"Show Me The Way" band
STYXRiver next to Hades
STYXWhere Charon rowed
STYX"Mr. Roboto" band
STYXRiver around Hades
STYXRiver of ferried dead
STYXCharon's river
STYXRiver of Hades
STYXMilton called it "the flood of deadly hate"
STYXIt goes around hell
STYXSouls of the dead cross it
STYXThe "river of Hate"
STYXIt's dubbed "the flood of burning hate" in "Paradise Lost"
STYXSite of a mythological ferry service
STYXThe souls of the dead crossed it, in myth
STYXRiver circling the underworld