Unknown Pendant

Why would they have left it on purpose?

There is another symbol on the back of it, but it's incredibly faint, I can hardly see it, so I don't know if it would appear on camera.

Try sensing what kind of energy flows thro it, always best to look at the symbol in context with its energy

If someone lived there that identified as heathen and they had died, or one ov their loved ones died, then it could have been left as a token ov respect to their spirit or to Odin in the hope that He would aid in carrying off the persons spirit.
The symbol marks my grandfathers grave, along with a few others.
If it was there before you were I would not remove it or ever wear it.
But it could have been a number ov things, not everything is spiritual or "supernatural" in occurrence.

I found it in a dirty corner covered in spiders, is this a normal place to leave such a thing? As far as the stories went, no one died in my room, thankfully.

It doesn't feel bad or evil, but has a strange energy, hard to place.