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. He can have up to 10 shapes in his memory if he wants new one he have to forget one of them.

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.

Greater shapeshift. as a action the Skar initiate an Inteligence contest with a any Humanoid that is within 5 ft and is icapacitated and isn´t protected by protection from evil and good. If Skar wins the contest he magicaly earn the shape and memories of the target he remember any memory, ability or spell that target had exept of pact and devine magic as long as using that shape. Doppelganger can have up to 5 Greater shapes if he want a new he have to forget one of his shapes.

Magic Resistence. The Skar has advantage on saving trows against spells and other magical effects.

Spellcasting. The Skar is a 10th-lavel spellcaster. Its spellcasting ability is Charisma (spell save DC 15, +8 to hit with spell attacks) The skar have following spells prepared:

Cantrips (at will): light, secred flame, thaumaturgy.

1st level (4 slots): detect magic, mage armor, magic missile, shield

2nd level (3 slots): hold person, suggestion

3rd level (3 slots): counterspell, lightning bolt, fireball.

4th level (3 slots): stone skin, banishment, ice storm

5th level (2 slots): cone of cold, wall of force

Multiattack. The doppelganger makes two melee attacks.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (1d10 + 6) bludgeoning damage.

Read Thoughts. The doppelganger magically reads the surface thoughts of one creature within 120 feet of it. The effect can penetrate barriers, but 6 feet of wood or dirt, 4 feet of stone, 4 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.

Limb change. In his true form Skar can polymorph one of his limb to limb of any humanoid that he have in his shape memory or grow a new limb. If the race that this limb originaly belonget to is natural wapon he gain a ability to attack with it dealing same damage as its original owner. If the limb is wing he gein 40 ft flying speed. Skar can have up to 8 limbs. He can retract one of them as bonus action.

Bone whip. Malee wapon Attack: +8 to hit reach 15 ft., one target, Hit: 18 (2d12+6) bludgeoing damage. And target must succadet in DC 16 Dexterity saving trow or be knocked prone.