Planar Bestiary
Stygian sleepfish are large aquatic predators of the River Styx. Because they can safely swim in the Styx, they hunt various kinds of fiends and have been known to attack those who cross the river in boats. Stygian sleepfish grow to be 30 feet (9 meters) long as adults, and larger specimens suggest that they continue to grow (at a slower pace) for as long as they live. They are sometimes used as mounts by especially vicious aquatic fiends, but this usually requires severing their tendrils on a regular basis so they don't strike their rider.
Sleepfish lurk in the depths of the Styx and its tributaries, and therefore can be found on any plane the river touches. They use their mouth tendrils to knock prey unconscious, then bite their sleeping foes to death. Their strong front fins allow them to emerge from the water and crawl if necessary, such as to cross a beach or sandbar or get around an obstacle.
Because they primarily consume demons, devils, and other fiends, sleepfish are generally inedible to humanoids.
A sleepfish can breathe air and move about on land, but they need to be submerged in water at least once every four hours to avoid suffocating.
Motive: Hungers for flesh
Environment: The River Styx, sometimes in riverways of worlds of the Material Plane, alone or in groups of three or four
Health: 15
Damage Inflicted: Minor wound (3 points)
Armor: 1
Movement: Immediate; short when swimming
Modifications: Speed defense in water as level 5 (due to agility and despite large size); Speed defense on land as level 3
Combat: The sleepfish charges into combat when possible, moving a short distance then making an eased bite attack that inflicts a moderate wound (6 points).
On rounds after their initial charging attack, the sleepfish attacks twice per round with their tendrils. Tendrils inflict damage and on a failed Intellect defense task, a victim falls asleep for a few minutes, or until they take damage or an ally uses an action to wake them early.
A sleepfish normally uses their poison, secreted from poison spurs, on sleeping targets so gradually and gently that they don't wake up but instead succumb forever. However, in combat against active foes, a sleepfish can make a melee attack with their spurs, inflicting 5 points of Speed damage (ignores Armor).
Interaction: Vicious and cunning, a sleepfish is about as intelligent as a shark. If one realizes they're overmatched, they swim away.
Use: A shipment of rare spices must travel upriver for some distance before reaching home port. After an unusually violent storm, several of the crew were pulled under the water by "monsters." The captain and remaining crew fled. Now the ship drifts along the river, full of valuable goods, but without anyone brave enough to reclaim it.
GM Intrusion: The sleepfish vomits up the head of a not-completely.digested demon. Necromantically animate, the head attacks a character and their allies.
Head of a demon (undead): level 3; swims a short distance each round; bite inflicts a moderate wound (5 points)