Centimaid

So Many Legs. The centimaid has advantage on rolls against being knocked prone.

Devouring Love.  The centimaid has advantage on attack rolls against creatures that are Charmed or Frightened by it and scores critical hits against them on a 19 or 20.

Shed Layer. The Centimaid sheds its exoskeleton dropping its armor class to 12 but increasing its movement speed by 20.

Chitter. The Centimaid rubs it's legs together to make an uncomfortable sound. Each creature within 30 feet that can hear it must succeed on a DC14 Constitution saving throw or be Frightened by the centimaid.

Enthralling Song (Recharge 5-6).  The Centimaid hums a debilitatingly beautiful song.  Each creature within 120 feet that can hear it must succeed on a DC14 Wisdom saving throw or be Charmed by the mermaid.  While charmed, the target is incapacitated and must use all its movement on its turn to move closer to the mermaid, regardless of hazards.  A charmed creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.  The song lasts for 10 minutes or until the Centimaid ends it willingly (no action required), falls unconscious, or loses concentration (as if concentrating on a spell).

Multiattack (Recharge 4-6). The centimaid makes two attacks, one with its bite and one with its claws.

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

Claws. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) slashing damage.

Venomous Spray (Recharge 5-6). 15 ft. cone, hit (1d10 + 2d4) acid damage.

Shed Layer. The Centimaid sheds its exoskeleton dropping its armor class to 12 but increasing its movement speed by 20.