Celestria

Incorporeal Movement. Celestria can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Mournful Melody. Celestria emanates a haunting song that can be heard within 120ft of her. Any creature starting its turn within its range must make a DC 13 Wisdom saving throw or become infected with her spectral plague, becoming unable to regain hitpoints, and coughing with consumption-like symptoms.

Withering Touch. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 17 (4d6 + 3) necrotic damage.

Horrifying Cry. Each non-undead creature within 60 feet of Celestria that can hear her must succeed on a DC 13 Wisdom saving throw or be frightened for 1 minute. If the save fails by 5 or more, the target also ages 1d4 × 10 years. A frightened target can repeat the saving throw at the end of each of its turns, ending the frightened condition on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to Celestria's Horrifying Cry for the next 24 hours. The aging effect can be reversed with a greater restoration spell, but only within 24 hours of it occurring.

Summon Mephits (Recharge 5-6). Celestria summons 1d4 Musical Mephits who act on their own initiative counts. They obey her telepathically, and are dispelled if she is incapacited or dies.

Cursed Touch. Whenever a creature targets Celestria with a melee attack, she can use her reaction to send forth cursed energy. The attacker must make a DC 13 Constitution saving throw. On a fail they become severely infected with the plague, gaining the poisoned condition and taking (1d6) necrotic damage at the end of each of their turns. A creature can repeat this saving throw at the start of each of their turns, ending the effect on a success.