Aura of Shrieks. Creatures within 20 feet of the grue that aren't Aberrations have disadvantage on saving throws, as well as on attack rolls against creatures other than a star spawn grue.

Confounding Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit:6 (2d4 + 1) piercing damage, and the target must succeed on a DC 10 Wisdom saving throw or attack rolls against it have advantage until the start of the grue's next turn.