Piercing Scream. Any creature that starts its turn within 5 feet of the Zombie Shrieker must succeed on a DC 12 Constitution saving throw or spend their action doing nothing as they are overwhelmed by the Zombie Shrieker's shrill scream. On a successful saving throw, the creature is immune to the Zombie Shrieker's Piercing Scream for 24 hours.

Shadow Stealth.  While in dim light or darkness, the Zombie Shrieker can take the Hide action as a bonus action.

Multiattack. The Zombie Shrieker makes two attacks, one with its bite and one with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage and 5 (1d10) necrotic damage.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 12 (2d6+5) slashing damage. If the target is a creatrue other than an undead, it must succeed on a DC 12 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on a success.