Tunneler. The worm can burrow through solid rock at half its burrow speed and can choose to leave a 10-foot-diameter tunnel in its wake.
Burrow Mastery. The worm moves through sand, stone, and earth without leaving a tunnel.
Hydrophobic. The worm will not willingly move through wet ground or come in contact with water. If the worm comes in contact with water, it must use its reaction to immediately move no less than 30 feet away from the source of water or the point of contact.
Titanic Form. The worm has advantage on saving throws vs being grappled, restrained, or knocked prone.
Siegebreaker. The worm deals double Damage to structures.
Legendary Resistance (3/Day)
Multiattack. The worm makes two attacks: one with its bite and one with its stinger.
Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 22 (3d8 + 8) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 17 Dexterity saving throw or be swallowed by the worm. A swallowed creature is blinded and its speed is 0. It has total cover against attacks and other effects outside the worm, and it takes 14 (4d6) acid damage at the start of each of the worm's turns.
If the worm takes 30 damage or more on a single turn from a creature inside it, the worm must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the worm. If the worm dies, a swallowed creature can escape from the corpse by using 20 feet of movement, exiting prone.
Tail Stinger. Melee Weapon Attack: +14 to hit, reach 15 ft., one creature. Hit: 19 (3d6 + 8) piercing damage, and the target must make a DC 21 Constitution saving throw, taking 18 (5d6) poison damage on a failed save, or half as much damage on a successful one.
Sand Charge. (Recharge 5–6). The worm makes a dash action and charges through the sand in a straight line. Each creature in the path must make a DC 17 Dexterity saving throw, taking 36 (8d8) bludgeoning damage on a failed save, or half as much damage on a successful one. A creature that fails the save is also prone.
Sand Surge. (Cost 2) The worm churns the ground in a 20-foot radius around itself. Creatures in that area must succeed on a DC 17 Dexterity saving throw or be blinded until the end of their next turn.
Tail Slam. (Cost 1) Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 20 (2d10 + 8) bludgeoning damage, and the target must succeed on a DC 17 Dexterity saving throw or be prone.
Burrow Shuffle. (Cost 1) The worm moves up to 25 feet through sand without provoking opportunity attacks.
Chittering Roar. (Cost 1) The worm emits a grinding, resonant roar. Each creature within 30 feet of the worm that is concentrating on a spell must succeed on a DC 21 Constitution ability check or immediately make a concentration check as if they had taken damage.
Lair and Lair Actions
Sand Sinkhole. Two creatures the worm sees must succeed on a DC 17 Dexterity save or sink 3 feet and become restrained.
Shifting Dune Cyclone. A 10-foot radius cylinder becomes a swirling sand vortex and becomes heavily obscured. Creatures inside must make a DC 17 Dexterity saving throw or take 3d6 bludgeoning damage and be blinded.
Dune Wall. A 20x40-foot sand dune rises, granting total cover and blocking line of sight. Creatures on the dune must make a DC 17 Dexterity saving throw or be knocked prone. The dune becomes difficult terrain.