Vorath, Dread Widow of The Silken Shroud

Ethereal Jaunt. As a bonus action, Vorath can magically shift from the Material Plane to the Ethereal Plane, or vice versa.

Spider Climb. Vorath can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Walker. The spider ignores movement restrictions caused by webbing.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: 18 (2d10 + 8) piercing damage, and the target must make a DC 14 Constitution saving throw, taking 36 (8d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.

Song of Serafina. Vorath sings a magical melody. Every humanoid within 300 feet of Vorath that can hear the song must succeed on a DC 11 Wisdom saving throw or be charmed until the song ends. Vorath must take a bonus action on its subsequent turns to continue singing. It can stop singing at any time. The song ends if Vorath is  incapacitated.

While charmed by Vorath, a target is incapacitated. If the charmed target is more than 5 feet away from Vorath, the target must move on its turn toward Vorath by the most direct route, trying to get within 5 feet. It doesn't avoid opportunity attacks, but before moving into damaging terrain, such as lava or a pit, and whenever it takes damage from a source other than Vorath, the target can repeat the saving throw. A charmed target can also repeat the saving throw at the end of each of its turns. If the saving throw is successful, the effect ends on it.

A target that successfully saves is immune the Song of Serafina for the next 24 hours.

Vorath 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. Vorath regains spent legendary actions at the start of its turn.

Web Strike (Costs 1 Action): The giant spider makes a web attack against a target within 10 feet. On a hit, the target is restrained by sticky webs. The restrained target can make a DC 14 Strength saving throw at the end of each of its turns, ending the effect on a success. Ranged Weapon Attack: +9 to hit, reach 10 ft., one creature.

Bite. (Costs 2 Actions): Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: 7 (2d10 + 8) piercing damage, and the target must make a DC 13 Constitution saving throw, taking 36 (8d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.