Basso Sylph

Dissonance. If the sylph takes damage whilst singing, it's song is disrupted, producing an agonizing discord. The creature that damaged the sylph takes an additional 3 psychic damage from Celestial Song until the beginning of its next turn. If more than one sylph is disrupted, this effect stacks. Damage from Dissonance cannot be reduced in any way save by immunity to psychic damage.

Silence Falls. When the sylph enters an area affected by a Silence spell, or starts its turn there, it is Paralysed until the beginning of its next turn.

Celestial Song. The sylph begins to sing.The sylph can use a bonus action on each of its turns to continue the song.

While the sylph sings, any creature that starts its turn within 300ft of the sylph must make a DC13 Wisdom saving throw, or take 2d4 thunder damage and become frightened until the start of its next turn. On a success, the target takes half as much damage and is not frightened.

Join Chorus. If an allied sylph within 30ft is currently singing, the sylph can instead unite their songs in chorus. For each additional sylph that joins the chorus, (up to a total of five including the original singer), the DC of the Wisdom saving throw increases by 1, and the Celestial Song deals an additional d4 Thunder damage. These effects apply in full to creatures within range of any of the sylphs.

If a sylph is ever more than 30ft from any other member of the chorus, the Joined Chorus ends.

Shield of Might. Melee Weapon Attack: +8 to hit, range 10 ft., one target. Hit: 10 (1d8+5) bludgeoning damage, and the target must succeed on a DC16 Constitution saving throw or be stunned until the end of its next turn.

Aegis. When a member of the chorus is hit with an attack, the basso sylph can interpose its shield to grant a +5 bonus to the target's AC. Once it does so, the basso sylph's AC decreases by 5 until it regains use of this reaction.

A chorus of sylphs has one legendary action, which can be used only at the end the turn of a creature not part of the chorus. The chorus regains spent legendary actions on initiative count 20.

If the basso sylph is part of a chorus, and is currently singing, the chorus gains the following legendary action:

Canto Praesidii. The basso sylph sings a rumbling, earth-shaking chant, warding another member of the chorus against harm. Until the start of that member's turn, it has resistance to all damage. If it normally has resistance, it is instead immune to that damage type. Whenever the warded creature takes damage, the basso sylph takes the same amount.