Doppel Mimics can speak, read, and write Common and Mimic. Another common language for mimics to know is Draconic due to them often being found in dragon's lairs.

Doppel Mimics typically begin their advanced level of thought at around the age of 50, this is just a blip in their life span, as they typically live to around 5 centuries old.

Doppel Mimics believe that a living beings are made up of all parts of the alignment spectrum so they do not see the use for it.

They look like the respective race they wish to take the form of.

Doppel Mimics take the appearance of the humanoid race they changed into and as, such take their appropriate sizes.

They take the movement speed of the race they are mimicking. Whether it is walking, running, swimming or flying.

You gain expertise in performance or deception and have a proficiency in Stealth.

You get a +2 and a +1 to put in whatever abilities you choose.

Because of the Doppel Mimics' race evolving in the dank and dark places of the world, they have an improved dark vision. You can see in dim light like it was bright light for 120 feet and dark light like it was dim light.

Doppel Mimics have adapted their skin and made it harder, granting them a base AC of 14 + their dexterity modifier. They can’t wear light, medium, or heavy armor, but if they are using a shield, they can apply the shield’s bonus as normal.

The Doppel Mimic has advantage on attack rolls against any creature grappled by it.

Whether you transform into an object or stay in your humanoid form, you can transform a part of your body into a large mouth and bite as an action. You can make a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use).

You succeed automatically if the target is incapacitated. If you succeed, you subject the target to the grappled condition. The condition specifies the things that end it, and you can release the target whenever you like (no action required).

The Doppel Mimic requires double the normal amount of food the race it's masquerading as does, to be satiated.

As an action the Doppel Mimic can open a large mouth on their body to consume a body of a large or smaller being. If the creature is still alive then they simply grapple them as they struggle. If a creature is consumed this way then the Doppel Mimic doesn't require food for 2 days but is still required to drink to survive.

Doppel Mimics are able to fit through gaps as small as 1 inch wide without squeezing.

By expending its action, the mimic is capable of transforming into an object or reverting to its natural humanoid state. In either form, its statistics remain constant, and any equipment it carries or wears remains unaffected. However, upon its death, the mimic automatically reverts back to its true form.

When you change into an object or person, roll a d20 and add your deception modifier, that will be the level of insight check needed to tell you apart from a normal object or person. (Repeat this roll every 10 minutes. Nat 20's only count as a DC 20 plus your deception modifier.)

You are able to turn into other people and take on their appearance, as well. If there is a "default" appearance that a Doppel Mimic takes, a appearance that they are often in and people know them by, they do not have to make this constant check to keep that appearance believable.

The Doppel Mimic adheres to anything that touches it. A large or smaller creature adhered to the mimic is also grappled by it (escape DC is 12 + your proficiency). Ability checks made to escape this grapple have disadvantage. 

(Only usable in object form.)

Doppel Mimics are able to climb walls with a movement speed of 25, ceilings count as rough terrain.