I don't know if this and appropriate place to put species info but I can't find anywhere else.

This is just a somewhat brief entry on my species 'Doppelgangers'. They are not open to be made but they aren't exactly closed either. They are just a species I've made up for my story and are part of its lore. So they aren't like Gatordog or Dutchies or anything to be openly distributed.

Doppelgangers; What are they?

If anyone has heard of the term, Doppelgangers are demons that are exact doubles of a specific person. They can have the same personality or an entirely different one, and this is essentially what these Doppelgangers are. They have existed since the beginning of the first life in the first created Universe. 

They do not reproduce like most species and instead are 'created'. No-one knows who created the 'first' doppelganger, but they have been creating more ever since. 

They live inside a planet that does not belong to any universe, but somehow exists between a plane that separates all of them; parallel and alternative universes included. It is likely they live inside the planet because there is literally nothing on or around it, but this also means that there is no way to or from the planet. The Doppelganger's have been able to find a way to travel to universes from the planet, but no-one who isn't a doppelganger can reach the planet by any known means.

How are they 'created'?

As mentioned above, no-one knows who created the first one, but they have since been able to create more in what are essentially 'growing pods'. Somehow, most likely due to their purpose, they have the means to create life without the need of parents. But what they do need is a source. The source being the person or creature that they are creating a double for. 

This of course isn't just limited to humans; they have every known universe they can pick their source from, meaning doppelgangers do not all look the same 'species'. For example, they might have some human doppelgangers, but also Krogen (from Mass Effect) doppelgangers, Sangheili (from Halo) doppelgangers and so on. They do not just pick any old species or person to clone, especially if created biologically (created in the growing pods), as they always have a purpose to being created.

Only recently however, they have been able to create doppelgangers 'robotically'. In this process they create a robotic-like reptilian looking pre-form. It is quicker than creating them biologically, and is much easier to control. These are called 'Reapers' and they all have a blade attached to their left arm in place of a hand and is usually longer than the arm itself. It is needed in order to create the doppelganger. There are two types of Reapers, simply dubbed Reaper v1.0 and v2.0. 

1.0 Reapers are much more robotic in appearance. They were the first to be made and still are but in fewer numbers. They tend to be smaller at an average height of 6'. The are easier to disable and kill altogether. 2.0 Reapers have a more life-like appearance which is due to having some biological elements added to their structure. They are considerably more intelligent and resourceful, and therefore harder to kill. They tend to overall be slightly larger at 6'6 average height. They can also summon their blade at will, and since it isn't attached they are almost impossible to disable. https://i.imgur.com/vg0sgPp.jpg

To become one, the Reaper would pierce the desired source (meaning they would need to go off-planet to the source's universe unlike the growing pods which they just need visual data). The blade would collect the DNA from the source and would essentially 'rip' apart the victim to which it would feed to the Reaper, in turn replacing it own DNA with the DNA of the source. This way the source is killed and cannot be recovered.

Biological/Robotic Key differences

Biological:

*Created in a pod, usually physically stronger and easier to modify.

*Longer to create; equates to 6 Earth months

*Does not replace the source, but inherently has the desire to kill them.

*Stronger will; more biologically similar to the source; risky as they can sometimes decided their own purpose.

Robotic:

*Starts off with the Reaper base

*Much quicker; Reapers take less than an Earth week to make and the transformation never lasts longer than a minute.

*Source is required to be present; can be risky if the source is skilled in combat as Reapers can be disabled before successful transformation.

*Source killed on the spot; already achieved its main goal.

*Cannot be modified once the Reaper has been replaced; somewhat weaker than the biological doppelganger. Weaker willed and follows orders without question.

A trait that is shared by all doppelgangers is their bright green eyes, so bright they can glow dimly in darkness. No matter the sources eye colour they are always green; as of yet they have not found a way to move around this small problem.

Because their anatomy is created exactly like their source only for effect, they do not necessarily need to eat, drink or rest. Depending on the species they copy would depend on how long they can go without and the consequences that come along with it.

Why do they exist?

If they had a better, more positive reason to exist, it has been lost a long time ago. Right now, the Doppelgangers desire total universe domination and want to replace everyone in it with their doppelganger counter-part, hence their desire to kill their source. 

Are there any traits specific to Doppelgangers? 

Doppelgangers are always meaner, evil versions of their source. They remove and replace positive traits with negative ones(e.g selfless sources will have selfish doppelgangers) and amplifys negative traits. They are usually stubborn, hot-headed and extremely aggressive. Some doppelgangers will have more developed personalities than others, but this is usually reserved for long-living and higher ranked ones. More defining traits are modesty; Sexual reproduction revolts them, and again depending on the source a massive pervert will have an extremely prudish doppelganger.