Bane Worm Juvenile

Tremor Sense. The Bane Worm can sense vibrations in the ground and detects creatures within 120 feet that are touching the ground. 

Legendary Resistance (1/Day). If the Bane Worm fails a saving throw, it can choose to succeed instead.

Innate Poison Resistance. The Bane Worm is naturally resistant to poison damage but not to being poisoned.

Burrower. The Bane Worm can burrow through earth and stone without disturbing the ground above. It leaves no tunnel behind, and any tunnels it creates collapse behind it.

Multiattack. The Bane Worm makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 32 (6d8 + 9) piercing damage. If the target is a Medium or smaller creature, it is swallowed by the Bane Worm. The swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the Bane Worm, and it takes 20 (6d6) acid damage at the start of each of the Bane Worm's turns. If the Bane Worm takes 40 damage or more on a single turn from a creature inside it, the Bane Worm must succeed on a DC 18 Constitution saving throw or regurgitate the swallowed creature. The swallowed creature falls prone in a space within 10 feet of the Bane Worm.

Tail. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 22 (4d8 + 9) bludgeoning damage.

Poison Spines (Recharge 5–6). The Bane Worm shoots a barrage of poisonous spines in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 20 Dexterity saving throw, taking 30 (8d6) piercing damage on a failed save, or half as much on a successful one. The creature must then succeed on a DC 20 Constitution saving throw or take 14 (4d6) poison damage. 

Earthquake (Recharge 6). The Bane Worm slams its body into the ground, causing a localized earthquake. Each creature within 60 feet of the Bane Worm must succeed on a DC 20 Dexterity saving throw or fall prone. Additionally, all structures within 100 feet of the Bane Worm are damaged, potentially collapsing if the DM deems the structures fragile or poorly built.

Evasive Burrow (Recharge 6). As a reaction, when targeted by an enemy attack, the Bane Worm may make a DC 15 Dexterity saving throw to avoid the attack and burrow into the ground using half of its movement speed.

The Bane Worm can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The Bane Worm regains spent legendary actions at the start of its turn.

Burrow. The Bane Worm burrows up to 40 feet without provoking opportunity attacks.
Tail Swipe. The Bane Worm makes a tail attack.
Tremor Step (Costs 2 Actions). The Bane Worm moves up to half its speed, causing tremors as it shifts. Each creature within 10 feet of the Bane Worm must succeed on a DC 18 Dexterity saving throw or fall prone.