Crawler Overlord

Acidic Touch. The crawler deals and extra 7 (2d6) acid damage when it hits with a melee weapon attack (included in the attacks).

Blood Frenzy. The crawler has advantage on attack rolls against any target that doesn't have all of its hit points.

Multiattack. The crawler uses Mad Laughter or if it can, and then makes four attacks: four with its claws or two with its bite and two with its tail

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) slashing damage.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage. If the target is a creature paralyzed by a crawler, it must succeed on a DC 13 Constitution saving throw. On a failure, the creature turns into a crawler larva. A remove curse or similar magic can reverse this. After 1d4-1 weeks, the crawler larva turns into a crawler. Once transformed in this way, only a wish can revert the creature to its true form.

Stinger. Melee Weapon Attack: +6 to hit, reach 10 ft., one creature. Hit: 5 (1d4 + 3) piercing damage plus 5 (2d4) poison damage. The target must succeed on a DC 13 Constitution saving throw or become poisoned. While poisoned, it is also incapacitated. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. 

Mad Laughter (Recharge 5-6). The crawler emits a hysterical, terrifying laugh. All creatures that can hear the crawler and are up to 120 feet away must make a DC 16 Wisdom saving throw or become frightened for 1 minute. While frightened, the creature must use all of its movement to go directly away from the crawler. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Thunderous Roar (Recharge 6). Each creature of the crawler's choice that is within 60 feet of the crawler and able to hear it must succeed on a DC 15 Constitution saving throw or take 55 (10d10) thunder damage, be knocked prone, and become incapacitated for 1 round. On a success, the creature takes half as much damage and is knocked prone, but not incapacitated.

Protect. The crawler adds 6 to the AC of a non-hostile creature up to 10 feet away when a melee attack would hit it.