There are countless scary stories all over the internet but there always seems to be 1 object in a large majority of stories that shows up.
The mirror this object has for some reason terrified people. But for what reason? I have been reading stories books Creepypastas yet it seems 1 out of every 100 or so online stories have mirrors. This has been a common theme for stories. Unfortunately I have not been able to find anything but stories with mirrors for example:

The images we see in the mirror are the pure incarnates of evil. They are only allowed to exist in the area reflected in the glass. To them, life is like a never-ending hell, rotting away in the same room day after day. The only refuse from this purgatory is death, and the only way for them to die, sad to say, is if YOU die. Fortunately, they are bound by a code. You are their master, and they must mirror your every movement and expression. To do otherwise would break an unbreakable law, unraveling the space-time continuum. However, there is a loophole, and it can only be triggered by you, the master. To force them into error is to free them from their contract; after you let them out of your view, you’re on your own. Know this: when you watch them, they’re watching you back. They’re watching. And they’re thinking.

See? this got a 7.5 out of 10 on creepypasta because for whatever reason there is a fear that when you're looking in a mirror there is someone (or something) staring back…

The mirror has been dated back to 6000 BC I Believe that since there are so many stories of mirrors now they would have a few about them back then though I'm not too too sure.