Wall Beholder

Expendable Tendrils. If the Wall Beholder loses one of its vine-like tentacles, it regrows another to full-length by the start of its next turn.

The Wall Beholder has advantage on rolls to initiate a grapple, but not to maintain it.  A creature can choose to use its action to cut the tendrils with any item that does slashing damage.

Rooted. The Wall Beholder is attached to the wall behind it and cannot move.

Self-Preservation. If the wall it is attached to is destroyed, the Off-the-Wall Beholder will use its tentacles to pull itself to safety.  Unless trapped and forced to fight, it will always flee once un-walled.

Transplant. The Wall Beholder can use its action to dig a recess into a new wall and crawl into it.  Once this is done, it needs a moment to dig its roots into the stone.  Until the Wall Beholder's next turn, it can't take any reactions.

Tentacle Whip. Melee Weapon Attack: +3 to hit, reach 25 ft., one target. Hit: 14 (4d6) slashing damage.

Eye Ray. The Wall Beholder uses a random magical eye ray, choosing a target that it can see within 60 feet of it.

1. Paralyzing Ray. The targeted creature must succeed on a DC 14 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

2. Fear Ray. The targeted creature must succeed on a DC 14 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

3. Enervation Ray. The targeted creature must make a DC 14 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one.

4. Disintegration Ray. If the target is a creature, it must succeed on a DC 14 Dexterity saving throw or take 45 (10d8) force damage. If this damage reduces the creature to 0 hit points, its body becomes a pile of fine gray dust.

If the target is a Large or smaller nonmagical object or creation of magical force, it is disintegrated without a saving throw. If the target is a Huge or larger nonmagical object or creation of magical force, this ray disintegrates a 10-foot cube of it.