Detect Life. The banshee can magically sense the presence of creatures up to 5 miles away that aren’t undead or constructs. She knows the general direction they’re in but not their exact locations.

Legendary resistance (2/Day). If the banshee fails a saving throw, it can choose to succeed instead.

Corrupting Touch. Melee Spell Attack: +9 to hit, reach 5 ft., one target. Hit: 25 (3d12+4) necrotic damage.

Horrifying Visage. Each non-undead creature within 60 feet of the banshee that can see her must succeed on a DC 16 Wisdom saving throw or be frightened for 1 minute. A frightened target can repeat the saving throw at the end of each of its turns, with disadvantage if the banshee is within line of sight, ending the effect on itself on a success. If a target’s saving throw is successful or the effect ends for it, the target is immune to the banshee’s Horrifying Visage for the next 24 hours.

Wail (1/Day). The banshee releases a mournful wail, provided that she isn’t in sunlight. This wail has no effect on constructs and undead. All other creatures within 30 feet of her that can hear her must make a DC 16 Constitution saving throw. On a failure, a creature drops to 0 hit points. On a success, a creature takes 24 (6d6) psychic damage.

Opportunity Attack

Can cast Shadow Ice Tomb on itself and take the damage and if the tomb holds until it's next turn she heals 25 hp

The Banshee can take 3 Legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Bellow (Costs 3 Actions). All creatures within 30 feet of the monster must make a DC (15) Constitution saving throw as the monster erupts in noise. On a failed save, a creature takes 5 (2d4) thunder damage and is deafened for 1 minute. A deafened creature can repeat the save at the end of their turns, ending the effect on a success. On a successful save, it takes half damage.

Banshee Barrage (Costs 1 action) The banshee can make an attack. Has advantage if they are frightene

The Banshee can take 3 Mythic actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

 Frightening Strike (Costs 2 actions). Creature is frightened of the banshee and they end there turn within 20ft. of the Banshee, it can move toward them without provoking opportunity of attack and make an extra attack on the frightened creature

 Shadow Ice Tomb ( Costs 3 Actions):
Range (60ft) Target must make a Con save(18). On a success they take 4d4 ice damage and con take any reactions or bonus actions on their next turn. On a failed save black ice erupts form the ground and surrounds the target forming an ice tomb, the ice has 25 hp and has an AC of 10 and is vulnerable to fire damage and bludgeoning damage. If you are in the tomb you make attacks to free yourself at disadvantage