A cerberus spawn is a large, three-headed dog. They usually have sleek, grey-brown fur, although some are jet black. One can often seen their veins, which glow like red-hot lava through their skin. Their eyes, too, glow red above their slavering maws.
Spawn of Hades. Cerberus spawn are said to be the get of Cerberus itself, the great hound who stands guard upon the gates of Hades. Like their forefather, cerberus spawn are used throughout Hades to keeps souls from escaping their gaols and masters.
Guard Dogs of the Lower Planes. From Hades, the cerberus spawn have spread throughout the Lower Planes, where many demons and devils employ them as guardians. Even wild packs are sometimes seen, roaming the Abyss, feasting upon the damned souls of Avernus, or adding their howls to the lamentations of Cocytus.
Ghost Hounds. The gifts of cerberus spawn are also renowned on the Material Plane, where their affinity for souls makes them expert trackers of ghosts and other incorporeal undead.
Packs of cerberus spawn are also often brought to the Material Plane by more powerful fiends. They are sometimes abandoned by these masters, or left feral after mortal heroes dispose of their keepers. Such hounds often seek a way home, although some find the easy prey of the mortal world to their liking and settle down.
Cerberus spawn breed true, but rarely (only going into heat once every thirteen years), so fortunately these packs rarely become endemic. Druids often seek to eliminate them, however, because they tend to violently displace native predators. (It’s not unusual, for example, to find dead wolves marking the limits of a cerberus spawn’s territory.)
CERBERUS SPAWN
Large fiend, neutral evil
Armor Class 15 (natural armor)
Hit Points 85 (10d10+30)
Speed 50 ft.
STR 22 (+6), DEX 9 (-1), CON 17 (+3), INT 8 (-1), WIS 12 (+1), CHA 5 (-3)
Skills Perception +5
Senses darkvision 60 ft., passive perception 15
Languages Infernal
Challenge 5 (1,800 XP)
Proficiency Bonus +3
Three Heads: A spawn has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.
Soul Scenter: A cerberus spawn gains advantage on Wisdom (Survival) checks related to ghosts and similar undead.
Magic Resistance. A spawn has advantage on saving throws against spells and other magical effects.
ACTIONS
Multiattack. The spawn makes three bite attacks.
Bite. Melee Weapon Attack. +9 to hit, reach 5 ft., one target. Hit: 17 (2d10+6) piercing damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.
Pretty nitpicky but the Perception skill bonus listed isn’t what you’d get from ability modifier + proficiency bonus. Is that a mistake or just a “It’s an NPC I can do what I want”?