Amphibious. The merfolk can breathe air and water.
Siren Song. Lovely singing voices charm every humanoid or giant within 300 feet. The targets must succeed on a DC 11 Wisdom saving throw or be charmed until the song ends.
Bite. Melee Weapon Attack: +2 to hit, one target. Hit:3 (1d6) piercing damage.
The Crystal Cave merfolk have long, flowing fins and silvery scales. They have lovely, melodic voices that are enhanced by the vibrating crystals of the cave in which they dwell.