The Styx (AND the River Lethe, River of Forgetfulness), unless things have changed over editions, flow through all planes including "worlds" of the Prime Material. The trick is FINDING it…so often folks travel to another plane because someone knows where it can be found there.
— Ed Greenwood (@TheEdVerse) September 4, 2018
Does the River Styx have a connection to the material plane (and where)?
