Blood Mermaid

Innate Spellcasting. The Blood Mermaid innate spellcasting ability is Charisma (spell save DC 17). It can innately cast the following spells, requiring no material components:

At will: alter self, major image

4/day each: charm person, detect thoughts, fear

2/day: synaptic static, ice knife

Magic Resistance. The Blood Mermaid has advantage on saving throws against spells and other magical effects.

Magic Weapons. The Blood Mermaid weapon attacks are magical.

Frenzy. When a Blood Mermaid attacks a creature that is not at full health, they attack at advantage.

Multiattack. The Blood Mermaid makes two attacks, one with its claws and one with its bite, or it casts one spell from its Innate Spellcasting trait and makes one claw attack.

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d8 + 3) piercing damage.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d8 + 1) piercing damage. If the target is a creature, it must succeed on a DC 16 Constitution saving throw or take 11 (2d10) poison damage and become poisoned for 1 minute. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Painful screech.  When damaged from a melee or ranged attack, the Blood Mermaid lets out a scream.  All creatures within a 15 ft radius must make a Wisdom saving throw (DC 17) or be stunned.