Copycat Doppleganger

Shapechanger. The Copycat Doppleganger 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, do not change in each form. Any equipment it is wearing or carrying isn't transformed. The Copycat Doppleganger reverts to its true form if it dies.

Learn. The Copycat Doppleganger can learn any spell or cantrip seen or cast upon him.

Production. The Copycat Doppleganger can produce any non-magical item or substance from its body.  If the item it is replicating is magical, the Copycat Doppleganger can create something appearing to be that item, without it's magical properties.

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

Surprise Attack. If the Copycat Doppleganger 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.

Multiaction. The Copycat Doppleganger takes two actions per turn.

Shapeshift. Change into anything it knows and can take on any all attributes of that object, creature, person. Takes one action.

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

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

Opportunity Strike. When an opponent moves out of melee range of the Copycat Doppleganger, the Copycat Doppleganger has the opportunity to make an attack of it's choice.