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A bad-tempered and highly adaptable alien gifted with rapid regeneration and three highly specialized forms among other things. Created in space from a virus that fused with a special meteor, they spent the first years of their life alone, without ever having seen another living thing. In those days their appearance was much further from humanoid, though they have no way of knowing this, having never glimpsed a reflective surface while in space. Though they were alone during this time with scarce material to interact with, it would not be until they stared the process of acclimating to terrestrial life that they knew "boredom" or "loneliness." They did however find some stimulus in exploding space debris with their Psycho Boost. The circumstance of their crash landing is rather unfortunate; a meteor they were resting on got pulled into the Earth's atmosphere. Before they knew what was happening they were plummeting toward a strange new world as their "flesh" burned away, leaving only their core. Upon landing they subconsciously took on physical characteristics of the planet's inhabitants; at least the external ones to begin with. 

The new arrival was dangerous and despised every aspect of the planet. They possessed no concept of restraint and regarded the people they saw as synonymous with the rocks they used to blow up for fun. They took a lot of lives before becoming overwhelmed by the sheer number of people in the world and going into hiding. During this time they taught themselves basic language out of curiosity. The turning point where they started viewing other living things as a little more than odd, ugly bits of debris was when they had a conversation with someone for the first time. Since then they have made massive improvement in a relatively short period of time.

At first they were prone to acts of violence that made interaction like walking barefoot through broken glass. Say or do the wrong thing and it was very likely they would lash out. The aggression stems not from some innate factor of their DNA, but rather the combination of lack of any form of socialization and frustration in their lack of understanding. Naturally they have mellowed out over time, having learned a great deal, though they are still known to have a very short temper. Their bullheadedness and limited socialization makes it trying to converse with them still. Because they now possess an adequate grasp of language, it is easy to forget that they are still incredibly immature emotionally and unable to process their own feelings most of the time let alone the feelings of others. Actions often contradict words and thoughts might contradict both (in other words they’re an internal mess). At the moment they are in the process of learning to appreciate the company of certain other people. 

Physiology

The Core

At the center of their chest is the green crystalline organ responsible for regulating every bodily function. It is by itself arguably their truest form, as they are capable of surviving without any other parts. This organ functions mostly subconsciously, performing tasks independently of thought, though it will also act according to the alien's will. That being said, the ultimate will of the core—self-preservation—is overpowering in a truly dire situation.

 Due to its role as the source of all function within this alien's body, the core is also their greatest weakness. Any damage done to it might have devastating consequences. In one case where a deep crack appeared from a fight, the alien experienced memory loss and periods of "death" where their body would shut down frequently at an alarmingly increasing rate and for increasing amounts of time. That being said, this core being their only weakness has its advantages as well. While this organ remains intact, it is impossible for the alien to be killed. They will regenerate indefinitely if harmed, though speed of regeneration depends on the amount of energy they have left (this is not typically an issue except in cases of repeated, consecutive limb loss, as they have a highly efficient method of acquiring energy). Even if this core were to be say, forcibly removed from its body, as long as it has sustained no damage, a new body will regenerate around it.

Other Organs

This alien does in fact possess most of the same organs as a human—though this has not always been the case. Their current body has adapted to terrestrial life by mimicking the lifeforms around it. Generated organs are completely functional but unnecessary. Their primary use is to take some of the burden off of the core, but if they ever become a nuisance the core will "switch them off" and take over; for instance, if a generated organ is punctured or otherwise damaged, the core has the ability to halt blood-flow or make it stop functioning until regeneration can occur.