Eyestalk of Gzemnid

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

The eyestalk attacks with its bite and uses Eradication Gaze.

Melee Weapon Attack +14 to hit, reach 10 ft., one target. 22 (3d8 + 9) Piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 19 Dexterity saving throw or be swallowed by the eyestalk. A swallowed creature is Blinded and Restrained, it has Cover against attacks and other effects outside the eyestalk, and it takes 21 (6d6) Acid damage at the start of each of the eyestalk's turns.
If the eyestalk takes 30 damage or more on a single turn from a creature inside it, the eyestalk 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 eyestalk. If the eyestalk dies, a swallowed creature is no longer Restrained by it and can escape from the corpse by using 20 feet of movement, exiting Prone.

The eyestalk creates an area of magical devastation in a 150-foot cone. Any creature in that area must succeed on a DC 16 Dexterity saving throw or take 55 (10d10) Necrotic damage. If this damage reduces a creature to 0 hit points, its body becomes a pile of fine violet dust.