Crystal Walker

Mirror Reflection. While moving through the crystals, the Walker can choose to embody the reflection of one creature. A DC 16 Perception check discerns that this reflection is slightly off and doesn't quite move in sync with the target. If a creature looks at their reflection, it can engage its Shapechanger ability. 

Shapechanger. The Walker forces one creature within 60ft to make a DC 16 wisdom save. If the creature fails, the Walker can emerge from its crystal prison and polymorphs into the creature. Its statistics, other than its size, are the same. It can also imitate the equipment the creature is wearing or carrying, in the form of an illusion. It reverts to its true form if it dies. 

Slash. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) slashing damage.

Psychic Link. When the Walker takes damage, the target it is linked to must make a DC 16 wisdom save. On a failure, the target takes damage equal to that taken by the Walker in the form of psychic damage. On a success, the damage is halved. The target observes a similar wound appear on their own body, though they are only illusions that will fade upon the Walker's death. The Walker may choose to injure itself as a method of attacking its target.

Penetrate Mind (recharge 5-6). The Walker can delve into the soul and mind of the creature it is embodying, dragging up a painful thought or memory and dealing 13 (3d8) psychic damage. The Walker enjoys using this information to mock its target's traumas, secrets, and fears.