Monster Monday: Hellmouth, the Gateway Monster

Today's Monster Monday is the hellmouth, a tremendous beast whose very mouth is a gateway to Hell (as you may have guessed from the name). Hellmouths were a motif in medieval art that tended to result in some pretty metal images, as in this detail from an icon showing a black hellmouth swallowing a bunch of damned souls, who are also simultaneously being roasted in flame, tortured by devils, and/or attacked by snakes:

Hellmouth, via Wikimedia

As it is statted up below, the hellmouth is not a monster the GM should use lightly. It is always important, when designing encounters, to take into account what might happen if one or more of the characters succumbs to the monster's powerful abilities. You don't want to throw a medusa at your players if you aren't prepared to spend some time with one or more of them petrified. Just so, you don't want to throw a hellmouth at your players if you aren't prepared to spend the rest of the session with half the part stuck in Hell. The hellmouth is best used when necessary as part of the story, rather than as a random encounter. That said, suddenly having to improvise a rescue mission to get your bard out of Hell sounds like a pretty fun session.

The hellmouth does not have to be a potential campaign derailer. If you aren't ready to randomly throw some of the PC into a screaming torture-dimension, the hellmouth can suppress its throat-gate, allowing it to simply swallow folks into its flaming stomach. It is also designed to act as a living infernal siege engine, launching flaming boulders at distant targets and calling in reinforcements from Hell.

By the way, I've decided to start giving some adventure hooks below each monster, so even if you don't feel like reading a stat block, scroll down for dem sweet hooks.

The following text in gold is available as Open Game Content under the OGL. Open Game Content is ©2017 Jonah Bomgaars.
This lumbering, scaled beast’s gaping mouth is filled with hellfire and brimstone

Devil, Hellmouth            CR 12

XP 19,200

LE Huge outsider (devil, evil, extraplanar, lawful)

Init +3; Senses darkvision 60 ft., see in darkness; Perception +21

Aura fear (20 ft., DC 21)

DEFENSE

AC 25, touch 7, flat-footed 25 (-1 Dex, -2 size, +18 natural)

hp 187 (15d10+105)

Fort +16, Ref +6, Will +14

DR 10/good; Immune fire, poison

Resist acid 10, cold 10; SR 23

OFFENSE

Speed 20 ft.

Melee bite +21 (2d8+12 plus grab)

Space 15 ft.; Reach 10 ft.

Ranged brimstone +12 (2d8+12 plus 2d6 fire) 80ft.

Special Attacks breath weapon (40 ft. cone, 8d10 fire damage, Reflex DC 24 for half, useable every 1d4 rounds), swallow whole (5d6 acid and 5d6 fire, AC 19, 18 hp)

Spell-Like Abilities (CL 12^th)

   1/day – plane shift (self only), summon (level 4: 1 barbed devil, 35%; 1 bone devil, 45%; 1d4 bearded devils, 75%; or 1d6 imps and 2d4 lemures, 90%), wall of fire

   3/day – dimension door, hold person (DC 17), magic circle against good

STATISTICS

Str 26, Dex 8, Con 25, Int 13, Wis 16, Cha 18

Base Atk +15; CMB +25 (+29 grapple); CMD 34 (38 vs trip)

Feats Improved Initiative, Improved Vital Strike, Iron Will, Lighting Reflexes, Power Attack, Vital Strike

Skills Bluff +17, Climb +21, Knowledge (engineering) +19, Knowledge (planes) +19, Perception +21, Sense Motive +21, Spellcraft +9, Stealth +4, Swim +21

Languages Celestial, Common, Draconic, Infernal; telepathy 100 ft.

SPECIAL ABILITIES

Breath Weapon (Su)

The hellmouth spews forth pure hellfire from its mouth. Half the damage dealt is fire, but the other half results directly from unholy power and is therefore not subject to being reduced by resistance to fire-based attacks.

Brimstone (Ex)

Once every 1d4 rounds, as a standard action, the hellmouth can regurgitate a Medium-sized boulder of burning brimstone and launch it as a ranged touch attack with a range increment of 80 ft.

Hellgate (Su)

When outside the plane of Hell, the hellmouth’s throat forms a permanent gate linked to Hell. Any creatures swallowed whole by the hellmouth while the gate is active are transported to a random location in Hell within one mile of the gate’s other end. The hellmouth can suppress its gate as a free action, allowing creatures in its mouth to be swallowed whole normally.

   Creatures travelling from Hell through the hellmouth’s gate emerge from the hellmouth’s mouth in an adjacent square. The hellmouth is aware of the creature type, approximate power level, and alignment of any creature that passes through its gate; although it cannot use that knowledge to prevent a creature’s instantaneous passage through the gate, it can make an attack of opportunity against any creature attempting to leave its mouth.

ECOLOGY

Environment any (Hell)

Organization solitary

Treasure standard

Hellmouths are one of the greatest weapons of the infernal armies. These lumbering beasts spew forth fire, brimstone, and other devils from their gaping maw, for their throat is actually a gateway to Hell. Hellmouths are bloated, grotesque creatures with gigantic heads that make up fully half of their body and toothy mouths that rarely close. These huge beasts are thankfully rare outside of Hell, but when they do appear, it usually heralds a diabolic incursion. The armies of Hell use hellmouths to establish a foothold in a world, then pour forth from the beast’s infernal gate. When not spewing forth demons, hellmouths are also used as tremendous living siege-weapons by Hell’s generals. But the appearance of a hellmouth on a plane does not necessarily mean an army of devils is on its way. Sometimes hellmouths take jaunts to other planes purely out of their own hunger.

Abyssal Maws: The Abyss breeds similar creatures known as abyssal maws. Abyssal maws are Chaotic Evil, have the demon, evil, extraplanar, and chaotic subtypes, have all the resistances and immunities of demons instead of those of devils, and retain their immunity to fire. Their Hellmouth ability is linked to the Abyss rather than Hell.

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Example adventure hooks involving the hellmouth:

• A hellmouth has been spotted in a nearby valley, and city officials fear it may signal an impending infernal incursion!
• The beloved captain of the guard encountered a hellmouth while out on patrol and was swallowed! You have to get swallowed into hell to rescue him before it is too late.
• A celestial citadel is under siege by a horde of demons, but if you slay one of their abyssal maws you may be able to get through their lines and bring some relief to the defenders.
• An eccentric wizard requires a significant sample of infernal brimstone for her research. You may be able to get some from a hellmouth if you can goad it into spitting at you.

-your damned d20 despot