Shapechanger. The doppelganger 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.

Ambusher. The doppelganger has advantage on attack rolls against any creature it has surprised.

Surprise Attack. If the doppelganger surprises a creature and hits it with an attack during the first round of combat, the target takes an extra 10 (3d6) damage from the attack.

Multiattack. The doppelganger makes two melee attacks.

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

Radiant Chain Whip. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 9 (1d8+4) slashing damage, as well as 2 (1d4) radiant damage.

Shortsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) slashingdamage.

Radiant Beam. Vhalak fires a beam of radiant light from its whip at a creature it can see within 30 ft. The creature, and all creatures within a 5' line must make a DC14 Dexterity saving throw or take 3d6 radiant damage, or half as much on a success. 

Unleash Incarnation. You can heighten your echo’s fury. Whenever you take the Attack action, you can make one additional melee attack from the echo’s position.

Read Thoughts. The doppelganger 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, the doppelganger can continue reading its thoughts, as long as the doppelganger's concentration isn't broken (as if concentrating on a spell). While reading the target's mind, the doppelganger has advantage on Wisdom (Insight) and Charisma (Deception, Intimidation, and Persuasion) checks against the target.

Echo Avatar. You can temporarily transfer your consciousness to your echo. As an action, you can see through your echo’s eyes and hear through its ears. During this time, you are deafened and blinded. You can sustain this effect for up to 10 minutes, and you can end it at any time (requires no action). While your echo is being used in this way, it can be up to 1,000 feet away from you without being destroyed.

Action Surge. (Recharge 6). Vhalak may take a second action on his turn. 

Ring of Darkness (1/day) Vhalak casts the Darkness spell from its ring. This darkness does not require concentration. 

Manifest Echo. You can use a bonus action to magically manifest an echo of yourself in an unoccupied space you can see within 15 feet of you. This echo is a magical, translucent, gray image of you that lasts until it is destroyed, until you dismiss it as a bonus action, until you manifest another echo, or until you’re incapacitated.

Your echo has AC 14 + your proficiency bonus (AC=17), 1 hit point, and immunity to all conditions. If it has to make a saving throw, it uses your saving throw bonus for the roll. It is the same size as you, and it occupies its space. On your turn, you can mentally command the echo to move up to 30 feet in any direction (no action required). If your echo is ever more than 30 feet from you at the end of your turn, it is destroyed.

You can use the echo in the following ways:

• As a bonus action, you can teleport, magically swapping places with your echo at a cost of 15 feet of your movement, regardless of the distance between the two of you.
• When you take the Attack action on your turn, any attack you make with that action can originate from your space or the echo’s space. You make this choice for each attack.
• When a creature that you can see within 5 feet of your echo moves at least 5 feet away from it, you can use your reaction to make an opportunity attack against that creature as if you were in the echo’s space.

Second Wind. As a bonus action, Vhalak recovers 1d10+7 HP.