This area is guarded by the Specter Lycaon Phlegyas, who also serves as the river's boatman. He attacks and defeats Shiryu and Hyoga when they attempt to cross the Styx, but Kanon, witnessing the previous battle, kills the Specter with one blow and takes his boat, taking with him the two Bronze Saints.
- The Styx is often confused with the Acheron river, due to the Styx being the more well known river. In mythology, the Styx also lacks a ferryman.
- Unlike Acheron Charon, Phlegyas's Surplice is not named after the river he has charge of. He also doesn't charge passengers a fee to cross.
- Appropriately for this circle, the name Styx means "hateful"; it is also a special river that was honored by Zeus after its nymph, also named Styx, protected him during the Titanomachy. Zeus made it the river by which all holy vows are sworn; those who break such vows instantly die. Even gods who break an oath made on the Styx enter a deathlike coma for several months. In another myth, the Nereid Thetis dipped her infant son Achilles in this river, which had the effect of making his body impervious to all weapons.
- This circle mirrors Dante's own version of the Styx in the Divine Comedy, even including the boatman Dante designated over this region. The only difference is the Styx was the fifth major region of Hell, rather than the fourth.
- Saint Seiya (debut)