A gigantic whale, twice the size of ship surfaces. Its dark gray flesh contrasts hideously with the yellowish-white of its underbelly. It cuts through the water with a short, gray- mottled gray dorsal fin with a sharp curve. Its enormous mouth is lined with nearly 600 teeth of white or pale ivory color.
Stygian Leviathan CR 21
XP 409,600
NE Colossal magical beast (aquatic, extraplanar)
Init +5; Senses blindsight 120 ft.; Perception +29
Environment River Styx
Organization solitary
Treasure none
The Stygian leviathan is the largest known creature swimming the River Styx. Very few inhabitants bother this monster and it has no known natural enemies.
It spends its time swimming throughout the Styx, gulping massive quantities of Stygian plants and aquatic life (such as fiendish octopi and fiendish krakens). Occasionally, it slips through a portal that leads to other planes – most often these portals carry it to the Material Plane. On the Material Plane, the Stygian leviathan doesn’t deviate from its course – it simply swims about devouring whatever happens to get in its way. Some, on the other hand, actively hunt aquatic animals, preferring their flesh to the other more mundane food these monsters usually consume.
These beasts are solitary creatures and no more than a single leviathan has ever been encountered at one time (thankfully). Mating and reproduction cycles and methods are unknown and have never been documented.
These monsters are hunted by demons and devils for their flesh, which is used for food. Also, the teeth of dead Stygian leviathans are sometimes taken and fashioned into weapons of war.
Stygian Leviathan from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene.