Chitinoid

Blindsight. The chitinoid can perceive its surroundings without relying on sight, using echolocation. It can't be blinded and is immune to the blinded condition.

Swooping Strike. The chitinoid can use its action to make a special attack with its wings. It flies up to its fly speed and can then make a single melee weapon attack against a creature within 5 feet of it as it passes by.

Poison Gas. The chitinoid can use its action to release a cloud of poisonous gas in a 15-foot radius centered on itself. Each creature in the area must make a DC 13 Constitution saving throw, taking 14 (4d6) poison damage on a failed save, or half as much damage on a successful one. At the end of its turn it can try to recharge this ability by rolling d6, below 5 it is a failure, and above 5 it's a success.

Multiattack. The chitinoid makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 11 (2d8 + 2) piercing damage.

Tail. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 8 (1d10 + 2) bludgeoning damage.