Brain Devourer Worm

Siege Monster. The devourer worm deals double damage to objects and structures.

Tunneler. The dedevourer worm can burrow through solid rock at half its burrow speed and leaves a 10-foot-diameter tunnel in its wake.

Legendary Resistance (3/Day). If the devourer worm fails a saving throw, it can choose to succeed instead.

Magic Resistance. The devourer worm has advantage on saving throws against spells and other magical effects.

Multiattack. The devourer worm makes two Claw attacks and one Slam attack. 

Stinger. Melee Weapon Attack: +10 to hit, reach 20 ft., one target. Hit: 25 (5d10 + 3) piercing damage. If this damage reduces the target to 0 hit points, the devourer worm kills the target by consuming the targets brain through the stinger.

Claws. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 24 (6d8 + 3) slashing damage.

Slam. Area Melee Attack: Range 10ft./Radius 20 ft. Creatures in the area must make a DC 19 Strength saving throw, taking 3d12 bludgeoning damage on a failed save, or half as much damage on a successful one. On a failed save, the target is knocked prone. 

Mind Blast (Recharge 5-6). The devourer worm magically emits psychic energy. Creatures of its choice within a 60 foot cone must succeed on a DC 20 Intelligence saving throw or take 5d10 psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

The Brain Devourer Worm can take 3 legendary actions, choosing from the options below. Only one legendary action at a time and only at the end of another creature's turn. The devourer worm regains spent legendary actions at the start of its turn. 

Claw. The devourer worm makes a claw attack.

Compulsion. The devourer worm targets one humanoid that it can see within 30 feet of it. If the target can see the worm, it must succeed on a DC 21 Wisdom saving throw or be magically charmed. On a failed save, the creature uses all of it's movement it's next turn to move as close to the devourer worm as possible. If a target's saving throw is successful, the target is immune to the worm's compulsion for the next 24 hours. 

Shatter Concentration (Costs 2 Actions). The devourer worm targets a creature under the effects of its Compulsion. The target's concentration on a spell it has cast or an ability it is maintaining ends, and the target takes 19 (3d12) psychic damage.