Amphibious. Falenous can breathe air and water, but cannot sing underwater.

Stormbound Oath. While within 120 feet of Falenous, the harpy has advantage on saving throws against spells and other magical effects. The Harpy is also immune to being charmed or frightened.

Flock Tactics. The harpy has advantage on attack rolls against a creature if at least one of the harpy’s allies is within 10 feet of the creature and isn’t incapacitated.

Death Cry. When the Harpy dies within 120 feet of Falenous, it lets out a shriek infused with the might granted by Falenous. Each creature within 30 feet of the Harpy must succeed on a Constitution saving throw of DC 14 or take 12 (3d8) thunder damage and be deafened until the end of it's next turn. On a successful save take half damage.

Multiattack. The harpy makes two attacks: one with it's talons, then may use Oath Melody.

Talons. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (2d4 + 3) slashing damage.

Oath Melody. The Harpy sings a warped version of their natural melodies. Each creature within 30 feet that can hear the harpy must succeed on a Wisdom saving throw of DC 12 or be frightened until the end of the song. The harpy must take an action on it's subsequent turns to continue singing at any time. The song ends if the harpy is incapacitated. If the creature can see Falenous, it makes the saving throw with disadvantage. 

Storm Lash (Recharge 4-5). The harpy hurls a bolt of storm-touched energy at a creature within 100 feet. Ranged Spell Attack: +5 to hit, one target. Hit: 18 (4d8) lightning damage.