Siph

Name pronounciation : "sih-f" like sifting. This is because he doesn't want people to easily connect the word Siphon with his nname.

Stats: Stronger in the dark, weaker in the light; more soul energy equals more stat power and depends on what monsters were siphoned from. HP (1 to 410); ATK (1 to 85); DEF (1 to 165); EXP (???); LV (8)
Note: the highpoint of stats are slowly rising due to the matter of his AU.

Very basic rundown: 

Siph was corrupted slightly by the void while working on a machine with Gaster. As time progressed on, he began to lose more and more soul power. Then he finds a way to siphon soul power from others, particularly through touch or attacks. Karmic retribution is a big player in this ability, and the void corruption in his soul allows for a more dangerous manner of using this attack.

 - Siph doesn't have to kill to gain life energy from others, but it can kill or make others exhausted.

 - The darker it is, the easier he can siphon energy due to the void's influence.

 - Anyone with energy being siphoned will become more and more tired. The rate of this depends how fast Siph is siphoning energy.

Personality: 

Siph has become very manipulative throughout the years after his corruption. He has been forced to do some very tricky mindgames with people to attain soul energy in some cases. Siph is also very closed off despite appearing friendly and welcoming at first glance. 

Siph still cares about his brother, and thus refuses to siphon energy from him unless the only alternative is Siph losing control and possibly killing his brother.

General Facts:

 - In his universe, Siph no longer goes by the name of Sans as he finds that person is hardly who he is anymore. The fact that his soul is corrupted plays into this idea.

- When he is too low on soul energy to sustain himself, he will lose control. Void shadows and tendrils will reach out from his body to mindlessly find a soul to consume energy from. They are mindless and thus do not care if people die. They will not stop until Siph has enough energy to sustain himself.

- When Siph first became corrupted, he had no understanding of how his powers worked. Thus, he's hurt a lot of people in his early days of existing how he is now, most often not on purpose. Hence the reason his LV is at 8.

- Siph cannot die unless he is in a space without true shadows and blocked from the void's ever constant presence. When placed in such a space, Siph will begin to dust slowly, but the rate of his dusting depends on what types of souls he's most recently siphoned from. Siph will dust because his soul is broken and only held together by the influence of the void.

- After finding out he's unable to die (unless in certain circumstances which he is unaware of), Siph has purposefully become very detatched from his emotions so he doesn't fall down from the guilt and become a monstrosity of mindless hunger. 

- Siph sustains himself only to protect others from the pain that will come should he give up entirely on himself.

- The voidy energy living within Siph is slowly corrupting anyone he comes into contact with. 5his creates a slow decline in sanity, humanity, and overall mental wellbeing. The void energy is merely spreading its influence for its own selfish purposes. There is no redeeming purpose for this. It simply does as it wants.