The Longmouth

"It isn't big. That's what everyone gets wrong. It's the size of a dog. It's just that when it opens its mouth, the mouth goes on." — A Denseshifter, in hand-signs, translated

The Longmouth is the reason nobody talks in the Dense.

Seen from outside, it is an unremarkable animal: low and hairless, about the size of a large dog, with a smooth grey hide, no eyes, and a wide, flat head that is mostly jaw. It moves in short silent rushes and then freezes, head tilted, for a long time.

The trouble is the inside. The Dense squeezes five hundred feet into every foot, and the Longmouth has taken that squeeze into its own body. Its jaw is a foot across. Its throat, once you're past the teeth, is five hundred feet long, and it climbs slightly uphill.

Behaviour

• Hunts by sound. Longmouths are blind and have no sense of smell worth mentioning. They hear everything: footsteps, breathing, a heartbeat if the heart is nervous enough. Speech carries furthest of all.
• Waits. A Longmouth can lie completely still for days, listening. Travellers who stop to rest in the Dense and start chatting are the usual prey.
• Doesn't chew. It swallows prey whole, and prey keeps living for some time inside the long throat. Denseshifters say you can sometimes hear a very faint voice calling from a Longmouth's open jaw.
• Avoids Denslings. Longmouths turn away from Densling rhythms, as though the sound is unpleasant.

The Longmouth

Medium monstrosity, unaligned

• Armor Class 14 (natural armor)
• Hit Points 110 (13d8 + 52)
• Speed 40 ft., climb 30 ft.

• Skills Stealth +8, Perception +6
• Damage Resistances thunder
• Condition Immunities blinded, deafened (while inside the Dense)
• Senses blindsight 120 ft. (sound only; blind beyond this radius and in magical silence), passive Perception 16
• Languages none
• Challenge 7 (2,900 XP)

Hears Everything. The Longmouth automatically detects any creature within 120 feet that speaks, casts a spell with a verbal component, or moves at more than half speed. Creatures that move at half speed or less and make no noise must be found with Wisdom (Perception) checks as normal.

Silence Is Blindness. Inside a silence spell, the Longmouth is blinded.

Actions

Multiattack. The Longmouth makes one Bite attack and, if it has a creature grappled, uses Long Swallow.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) piercing damage, and the target is grappled (escape DC 15).

Long Swallow. The Longmouth swallows a Large or smaller creature it is grappling. A swallowed creature is blinded and restrained at the bottom of a 500-foot throat, has total cover against attacks from outside, and takes 10 (3d6) acid damage at the start of each of the Longmouth's turns. The throat can hold any number of creatures. A swallowed creature can climb 30 feet towards the jaw per turn with a DC 14 Strength (Athletics) check, and escapes out of the mouth when it reaches the top. If the Longmouth dies, all swallowed creatures are expelled, prone, next to the body, having crossed 500 feet in an instant.