Paintie by me
N/A, The Void is ageless
N/A, The Void can be whatever height/length it wishes
The Void started out as a computer virus that would simply erase files. Over time, it changed into something worse. Eventually, it was able to not only infect computers and erase files, but it was able to get inside any and all kinds of electronics and completely erase the device's ability to function. It wouldn't damage it physically or electronically in any way, and it wouldn't delete files- it just made whatever it infected devoid of functionality, hence being called The Void.
Finally, its abilities evolved to the point where it was able to possess anything that uses electricity in order to function, including living things. However, its effects on living, conscious beings are different...
When a Void possesses you, it forces you to think of things that you would never want to think of. Thoughts about people, things that you never want to see, that you never want to imagine. The Void can lay dormant in your mind for months, only to strike suddenly when it finds something important to you. It strikes sometimes without warning, and other times you will be able to feel it pulling you towards the things it tries to make you think of.