Amorphous. The shadow can move through a space as narrow as 1 inch wide without squeezing.

Shadow Stealth. While in dim light or darkness, the shadow can take the Hide action as a bonus action.

Sunlight Weakness. While in sunlight, the shadow has disadvantage on attack rolls, ability checks, and saving throws.

Mirthful Laughter: Any humanoid that starts its turn within 5 ft of the Youthful Shadow must make a DC 12 Charisma save or be charmed by it until the start of their next turn

Shadow's Embrace. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (2d6 + 1) necrotic damage. On a hit the shadow latches onto the target and can use its reaction to move with the target. 

When a creature is hit by Shadow's Embrace, the Youthful Shadow can use its reaction to move with the creature until the start of the Youthful Shadow's next turn.