Cave Siren

The creature is always the parties level, the creature gains 50% HP mod per level and +1 to attacks for every 4 levels remove the damage bonus and replace it with an extra dice (if an attack does 1d6 it now does 2d6) and +1 AC and to main stat)

.Spellcasting. The Siren is a 3-level spellcaster. Its spellcasting ability is CHA (spell save DC 16, +6 to hit with spell attacks).
Cantrips (at will): Lure,  The target must make a charisma saving throw on a fail next turn the player will  turn against their own team for 2 turns after which they will return and Lure cannot be used while its active and one turn after it wears off. On a fail nothing happens

Claw Swipe. Melee Weapon Attack: +5 to hit, reach 5ft.,# target. Hit:  (2d8 + 2) slashing damage. 

Scream. Ranged Weapon Attack: +4 to hit, range 50ft cone. Hit:  (1d8 + 3) piercing + (1d4+ 2) stress damage.

Call. At half HP the Siren screeches for help getting a Bone Defender to help.