Large beast, neutral evil

Armor Class 16 (natural armor)
Hit Points 97 (15d10+15)
Speed fly 60 ft.

17 (+3) 13 (+1) 12 (+1) 7 (-2) 10 (+0) 6 (-2)

Skills Stealth +4
Condition Immunities blinded, Petrified, prone
Damage Resistances lightning
Senses tremorsense 60 ft.
Challenge 6 (2300 XP)


  • Passwall. The yrth can cast passwall at will as an action.
  • Camouflage. The yrth naturally blends into any stone around it, giving it advantage on all Stealth checks.


  • Multiattack. The yrth can strike twice with its tentacles, and then once with its bite.
  • Tentacle. Melee Weapon Attack: +6 to hit, reach 15 ft., one creature. Hit: 10 (2d6+3) bludgeoning damage. The target must also make a Dexterity save (DC 15), taking 17 (5d6) lightning damage on a failed save, or half as much on a success.
  • Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 16 (2d12+3) piercing damage.


The yrth are creatures that dwell underground. They are long, flat, and wide with huge heads. Sores of fangs fill their wide jaws, these fangs never quite fit into the mouth when it’s closed.

Hard skin around the mouth bears the marks of their own teeth-ruts, carved from years of holding their jaws clamped shut. Long tendrils hang around the beast’s mouth; they are constantly moving, gyrating in the air before the creature. Along their back is a low ridge of flat bone that continues to the end of the beast’s tail. The tail itself sports a large, horizontal fin that provides the creature with its forward motion. The yrth have no eyes or nose.

Fly through Stone. The yrth are strange creatures that swim through the air as a fish does water. They rarely touch the ground. They move from cavern to cavern through an innate passwall ability, spending their entire lives in darkness. They feel their way through a host of small pits lining their head and along the boney apertures along their flanks. These serve as very primitive sonar similar to the bats.

Territorial. The yrth find a habitable den and nest there until forced out or slain. Their dens usually consist of fissures or holes beneath ledges, rocks, or outcroppings. They spend much of their lives in a dormant state, without the need of any nourishment. But they do not sleep and are constantly aware of what is going on around them.

Ambush. The yrth attack any potential prey that passes in front of their den. They begin their attack by whipping a tendril out to strike the prey with the electrical shock. They quickly follow the shock attack by lunging from their den and delivering a nasty bite. They continue to shock and bite until the prey is dead at which point they drag it into the den and devour it.

Section 15: Copyright Notice

5th Edition Monsters & Treasure of Airhde, 1st Printing, Copyright 2021, Troll Lord Games; Author Stephen Chenault & Jason Vey

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