bonecrusher

Amorphous. Bonecrusher can move through a space as narrow as 1 inch without squeezing.

Spider Climb. Bonecrusher can climb difficult surfaces, including ceilings, without an ability check.

Multiattack: the bonecrusher makes 4 attacks per round:

Bone-softening Pseudopod x1: Melee weapon attack: +9 to hit, reach 5', one target. Hit: On a failed DC15 Constitution save, 6d6+7 necrotic damage. Half as much on a successful save. On a failed save, the target's bones are softened and the target is now vulnerable to bludgeoning damage, until restored by Greater Restoration or a long rest.

Acid Sphere x3: Range weapon attack: +4 to hit, range 20/60', one target. Hit: 4d10+4 acid damage.

Disintegrate If the Bonecrusher is struck by a non-magical melee weapon by a creature within 5', the attacking creature must roll a DC17 Dexterity save. On a failure, the weapon is absorbed and dissolved after dealing damage.