The shadow fey has advantage on saving throws against being charmed, and magic can’t put it to sleep.

When three pattern dancers are within 60 feet of each other, they can work together to cast communal spells that are more powerful than they could cast individually. To do this, one takes an action to cast a spell, and the other two must use their reactions to complete it. These communal spells are cast at 11th level and have a spell save DC of 13:

At will: hold person

3/day: fear, sleep

1/day: confusion, hypnotic pattern

As a bonus action while in shadows, dim light, or darkness, the shadow fey disappears into the darkness and reappears in an unoccupied space it can see within 30 feet. A tendril of inky smoke appears at the origin and destination when it uses this trait.

While in sunlight, the shadow fey has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

The shadow fey has advantage on Intelligence (Arcana) checks made to know about shadow roads and shadow magic spells or items.