Waldemar, Child of Dark Reflections

Steal Shape. Waldemar can use its action to polymorph into a Small or Medium humanoid it has seen, or back into its true form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Psychic Ambusher. Waldemar has advantage on attack rolls against any creature it has surprised or whose shape it has stolen.

Sneak Attack. If Waldemar surprises a creature and hits it with an attack, or it has advantage on an attack for the first time each round, the target takes an extra 17 (5d6) damage from the attack.

Evasion. If Waldemar is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, Waldemar instead takes no damage if it succeeds on the saving throw, and only half damage if it fails. 

Multiattack. Waldemar makes two melee attacks.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) bludgeoning damage.

Read Thoughts. Waldemar magically reads the surface thoughts of one creature within 60 feet of it. The effect can penetrate barriers, but 3 feet of wood or dirt, 2 feet of stone, 2 inches of metal, or a thin sheet of lead blocks it. While the target is in range, Waldemar can continue reading its thoughts, as long as Waldemar’s concentration isn't broken (as if concentrating on a spell). While reading the target's mind, Waldemar has advantage on Wisdom (Insight) and Charisma (Deception, Intimidation, and Persuasion) checks against the target.

Cunning Action. On each of its turns, Waldemar can use a bonus action to take the Dash, Disengage, or Hide action.

Psychic Distortion. Waldemar wrenches the senses of an attacker it can see. Waldemar can choose to either impose disadvantage on the attack or force the attacker to target a creature within 5’ of it. If it attempts to redirect the attack, the attacker rolls a Wisdom Saving Throw (DC 16), attacking as normal on a success.

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

Lash Out. Waldemar makes a melee attack against any creature within reach.

Personal Space. (Costs 2 Actions) Waldemar screams, unleashing a tidal shove against each creature within 5’ of it. Affected creatures make a DC 16 Strength Saving Throw or are shoved 5’ and fall Prone.

I Saw It First. (Costs 3 Actions) Waldemar attempts to wrench control of an ongoing spell. The caster must make a DC 14 Concentration Check or Waldemar steals the effects. If a creature has a reaction available, they can choose to drop the spell before making a Concentration Check.

When Waldemar is reduced to 0 hit points for the first time each day, he regains half his maximum hit points and gains the effects of the Mirror Image spell. At the end of each round, a Mirror Image shatters and restores 2d8 + 4 hit points to Waldemar if at least one remains.

Moonshadow Warp. Waldemar casts Misty Step, but only from an area of darkness to another area of darkness.

Sinister Split. Waldemar gains an additional Mirror Image.

Share My Agony. (costs 3 actions) Waldemar chooses a creature it can see within 30’. That creature makes a DC 14 Charisma Saving Throw. On a failure, Waldemar steals their appearance, then average both creatures’ hit points. Until Waldemar’s next turn, damage is shared between it and the target, rounded down.