You are able to see as far as possible into the darkness. When in dim light, you treat it like normal light. When in darkness, you treat it like dim light. 

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.

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

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

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.

As a Doppelganger, your Charisma increases by 2 and your Dexterity increases by 1.