Chthonian (5e Creature)
From D&D Wiki
Huge aberration, neutral
Saving Throws Str +10, Con +9, Wis +5
Mind Net. While telepathically speaking with other members of its species on the same plane of existence, the chthonian's telepathy has unlimited range.
Tunneler. The chthonian can burrow through solid rock at its burrow speed and leaves a 5-foot diameter tunnel in its wake.
Water Hypersensitivity. The chthonian takes 30 acid damage when it starts its turn submerged in water. While in water, it has disadvantage on attack rolls and ability checks.
Multiattack. The chthonian makes two attacks, one with its tentacles and one with its slam.
Tentacles. Melee Weapon Attack: +10, reach 5 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage.
Earthquake (1/Day). The chthonian causes an earthquake in a 100-foot radius around it. The earthquake lasts as long as the chthonian maintains concentration, up to 1 minute (as if concentrating on a spell). The ground in the area turns into difficult terrain. Each creature on the ground that is concentrating must succeed on a DC 15 Constitution saving throw, or else the creature's concentration is broken. At the end of each of the chthonian's turns, each creature on the ground must succeed on a DC 15 Dexterity saving throw or be knocked prone. Caves or tunnels in the area will collapse. Creatures under the cave-in must succeed on a DC 15 Strength or Dexterity saving throw (target's choice). The cave-in causes 14 (4d6) bludgeoning damage, or half as much on a successful save. On a failed save, the target is buried in the rubble, and needs to succeed on a DC 17 Strength (Athletics) check as an action to escape. On open ground, there is an equal chance to take the same amount of damage from falling into a fissure, also needing a Strength check to climb back out. The earthquake also deals 20 bludgeoning damage to structures on the ground at the end of each of the chthonian's turns. Structures that drop to 0 hit points collapse. Creatures close to the collapsing structure have a chance of being hit, damaged and buried by rubble equal to the chance of being affected by the cave-in. Other chthonians are not affected by the earthquake. For each additional adult chthonian that joins the chthonian, the earthquake's radius is extended by 50 feet and structures in the area take an additional 10 bludgeoning damage each turn.
Worm Charm. The chthonian targets a creature within 60 feet of it. The target must succeed on a DC 15 Wisdom saving throw or be charmed by the chthonian. The charmed target obeys the chthonian's telepathic commands. If the target suffers any harm or receives a suicidal command, it can repeat the saving throw, ending the effect on a success. The chthonian can have only one target charmed at a time. If it attempts to charm another creature, the effect on the previous target ends.
Rage of the Earth (1/Day). When the chthonian is reduced to half its maximum hit points (103 hit points) or less, all Large or smaller creatures within a range of 30 feet of the chthonian must make a DC 15 Strength saving throw. On a failed save, a creature takes 9 (2d8) bludgeoning damage and is knocked prone. On a successful save, a creature takes half as much damage and isn't knocked prone. Other chthonians are not affected.
The chthonians resemble giant worms with a squid-like head with a mass of tentacles reminiscent of the dreaded Cthulhu, though they are not evil. Its huge body is covered by noisome secretions. The chthonian can, sometimes together with other members of its species, manipulate the crust of the planet in a fashion not understood. The chthonian avoids water, but is said to be completely immune to any form of heat and can even resist lava.