Corrosion Crawler Queen

False Appearance. When the queen is dormant, she is indistinguishable from a stone wall.

Corrosive Form. A creature that touches the corrosion crawler queen or hits it with a melee attack while within 5 feet of it takes 3 (1d6) acid damage. Any nonmagical weapon that hits the corrosion crawler queen corrodes. After dealing damage, the weapon takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed.

Nonmagical ammunition that hits the corrosion crawler queen is destroyed after dealing damage.

Frightful Shriek. Each creature of the corrosion crawler queen's choice that is within 60 feet of the corrosion crawler queen and aware of it must succeed on a DC 13 Wisdom saving throw or become frightened  and deafened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the corrosion crawler queen's Frightful Shriek for the next 24 hours.

The shriek can be heard for 600 ft. 

Any corrosion crawler larva that can hear the shriek drops to the ground and deals 3 (1d6) acid damage to any creature occupying the same space.

Any corrosion crawler pupa that can hear the shriek immediately attempts to Hatch.  On a failed Hatch attempt, the pupa dies in a Corrosive burst.

Any corrosion crawler that can hear the shriek uses it's full movement to come to the corrosion crawler queen's aide.

Multiattack the corrosion crawler queen makes up to 4 of it's slash attacks.

Slash. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 10 (2d6 + 3) slashing damage plus 3 (1d6) acid damage.

Corrosive Spray (Recharge 6).  Every creature in a 15 ft cone suffers 3d6 acid damage, if they succeed on a DC 13 Dexterity saving throw they take half this damage.  Any nonmagical weapon or armor in the area if effect that is unattended, or that is carried or worn by a creature that failed its save corrodes and takes a permanent and cumulative -1 penalty to it's damage roll or AC.  Any weapon who's damage bonus is reduced to -5 or armor who's AC bonus has been reduced to 10 is destroyed.